diff --git a/clean_files.txt b/clean_files.txt
index 8bfc2b0e7c..e3100b91e3 100644
--- a/clean_files.txt
+++ b/clean_files.txt
@@ -25,6 +25,7 @@ plugins/
 scripts/
 template/
 test/
+themes/
 
 # root files
 #
@@ -35,60 +36,6 @@ install.sh
 lint_clean_files.sh
 uninstall.sh
 
-# themes
-#
-themes/90210
-themes/agnoster
-themes/atomic
-themes/axin
-themes/bakke
-themes/barbuk
-themes/binaryanomaly
-themes/bira
-themes/bobby
-themes/bobby-python
-themes/brainy
-themes/brunton
-themes/candy
-themes/clean
-themes/codeword
-themes/cooperkid
-themes/cupcake
-themes/demula
-themes/dos
-themes/doubletime
-themes/doubletime_multiline
-themes/doubletime_multiline_pyonly
-themes/dulcie
-themes/duru
-themes/easy
-themes/elixr
-themes/emperor
-themes/envy
-themes/essential
-themes/font
-themes/gallifrey
-themes/gitline
-themes/hawaii50
-themes/inretio
-themes/iterate
-themes/kitsune
-themes/lambda
-themes/liquidprompt
-themes/luan
-themes/modern
-themes/norbu
-themes/oh-my-posh
-themes/p4helpers.theme.bash
-themes/pete
-themes/powerline
-themes/powerline-multiline
-themes/powerline-naked
-themes/pure
-themes/purity
-themes/rjorgenson
-themes/robbyrussell
-
 # vendor init files
 #
 vendor/.gitattributes
diff --git a/themes/atomic/atomic.theme.bash b/themes/atomic/atomic.theme.bash
index c59dbdc9b2..ba5410e098 100644
--- a/themes/atomic/atomic.theme.bash
+++ b/themes/atomic/atomic.theme.bash
@@ -118,7 +118,7 @@ function ___atomic_prompt_user_info() {
 
 function ___atomic_prompt_dir() {
 	local color="${IRed?}"
-	local box="[|]${normal}"
+	local box="[|]${normal?}"
 	local info="\w"
 	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white?}" "${box}"
 }
@@ -276,8 +276,8 @@ RBFU_THEME_PROMPT_SUFFIX=""
 RVM_THEME_PROMPT_PREFIX=""
 RVM_THEME_PROMPT_SUFFIX=""
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
 
 : "${THEME_SHOW_SUDO:="true"}"
 : "${THEME_SHOW_SCM:="true"}"
diff --git a/themes/axin/axin.theme.bash b/themes/axin/axin.theme.bash
index 7e90aded31..31cbf9a958 100644
--- a/themes/axin/axin.theme.bash
+++ b/themes/axin/axin.theme.bash
@@ -33,6 +33,6 @@ function prompt_command() {
 	PS1="\[${BOLD}${MAGENTA}\]\u \[$WHITE\]@ \[$ORANGE\]\h \[$WHITE\]in \[$GREEN\]\w\[$WHITE\]\[$SCM_THEME_PROMPT_PREFIX\]$(clock_prompt) \[$PURPLE\]$(scm_prompt_info) \n\$ \[$RESET\]"
 }
 
-THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"${white}"}
+THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"${white?}"}
 
 safe_append_prompt_command prompt_command
diff --git a/themes/bakke/bakke.theme.bash b/themes/bakke/bakke.theme.bash
index a3670b070f..7840787bca 100644
--- a/themes/bakke/bakke.theme.bash
+++ b/themes/bakke/bakke.theme.bash
@@ -15,9 +15,9 @@ RVM_THEME_PROMPT_PREFIX="|"
 RVM_THEME_PROMPT_SUFFIX="|"
 
 function prompt_command() {
-	#PS1="${bold_cyan}$(scm_char)${green}$(scm_prompt_info)${purple}$(ruby_version_prompt) ${yellow}\h ${reset_color}in ${green}\w ${reset_color}\n${green}→${reset_color} "
-	#PS1="\n${purple}\h: ${reset_color} ${green}\w\n${bold_cyan}$(scm_char)${green}$(scm_prompt_info) ${green}→${reset_color} "
-	#PS1="\n${cyan}\h: ${reset_color} ${yellow}\w\n${red}$(scm_char)${red}$(scm_prompt_info) ${green}→${reset_color} "
+	#PS1="${bold_cyan?}$(scm_char)${green?}$(scm_prompt_info)${purple?}$(ruby_version_prompt) ${yellow?}\h ${reset_color?}in ${green?}\w ${reset_color?}\n${green}→${reset_color?} "
+	#PS1="\n${purple?}\h: ${reset_color?} ${green?}\w\n${bold_cyan?}$(scm_char)${green?}$(scm_prompt_info) ${green}→${reset_color?} "
+	#PS1="\n${cyan?}\h: ${reset_color?} ${yellow?}\w\n${red?}$(scm_char)${red?}$(scm_prompt_info) ${green?}→${reset_color?} "
 	local virtualenv_prompt scm_prompt_info
 	virtualenv_prompt="$(virtualenv_prompt)"
 	scm_prompt_info="$(scm_prompt_info)"
diff --git a/themes/barbuk/barbuk.theme.bash b/themes/barbuk/barbuk.theme.bash
index 46b37e2b7e..69957bc730 100644
--- a/themes/barbuk/barbuk.theme.bash
+++ b/themes/barbuk/barbuk.theme.bash
@@ -88,7 +88,7 @@ function __exit_prompt() {
 	if [[ "$exit_code" -ne 0 ]]; then
 		echo "${purple?}${EXIT_CODE_ICON}${yellow?}${exit_code}${bold_orange?} "
 	else
-		echo "${bold_green}"
+		echo "${bold_green?}"
 	fi
 }
 
@@ -168,7 +168,7 @@ function __path_prompt() {
 		dir_color=${red?}
 	fi
 
-	echo "${dir_color}\w${normal} "
+	echo "${dir_color}\w${normal?} "
 }
 
 function __scm_prompt() {
@@ -197,7 +197,7 @@ function __prompt-command() {
 		wrap_char="\n"
 	fi
 
-	PS1="${PS1}${wrap_char}❯${normal} "
+	PS1="${PS1}${wrap_char}❯${normal?} "
 }
 
 safe_append_prompt_command __prompt-command
diff --git a/themes/binaryanomaly/binaryanomaly.theme.bash b/themes/binaryanomaly/binaryanomaly.theme.bash
index 3501e8d469..dacc8c93eb 100644
--- a/themes/binaryanomaly/binaryanomaly.theme.bash
+++ b/themes/binaryanomaly/binaryanomaly.theme.bash
@@ -58,17 +58,17 @@ function prompt_command() {
 	ps_reboot="${bright_yellow?}${show_reboot_required}${normal?}\n"
 
 	set_user_color="$(set_user_color)"
-	ps_username="${set_user_color}\u${normal}"
-	ps_uh_separator="${dark_grey?}@${normal}"
+	ps_username="${set_user_color}\u${normal?}"
+	ps_uh_separator="${dark_grey?}@${normal?}"
 	set_host_color="$(set_host_color)"
-	ps_hostname="${set_host_color}\h${normal}"
+	ps_hostname="${set_host_color}\h${normal?}"
 
-	ps_path="${yellow?}\w${normal}"
+	ps_path="${yellow?}\w${normal?}"
 	scm_prompt="$(scm_prompt)"
 	ps_scm_prompt="${light_grey?}${scm_prompt}"
 
-	ps_user_mark="${normal} ${normal}"
-	ps_user_input="${normal}"
+	ps_user_mark="${normal?} ${normal?}"
+	ps_user_input="${normal?}"
 
 	# Set prompt
 	ps_time="$(__ps_time)"
diff --git a/themes/brainy/brainy.theme.bash b/themes/brainy/brainy.theme.bash
index b93c768f56..1a1570ac3f 100644
--- a/themes/brainy/brainy.theme.bash
+++ b/themes/brainy/brainy.theme.bash
@@ -90,59 +90,59 @@ ____brainy_bottom() {
 ##############
 
 ___brainy_prompt_user_info() {
-	color=$bold_blue
+	color=${bold_blue?}
 	if [ "${THEME_SHOW_SUDO}" == "true" ]; then
 		if sudo -vn 1> /dev/null 2>&1; then
-			color=$bold_red
+			color=${bold_red?}
 		fi
 	fi
 	box="[|]"
 	info="\u@\H"
 	if [ -n "${SSH_CLIENT}" ]; then
-		printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white}" "${box}"
+		printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white?}" "${box}"
 	else
 		printf "%s|%s" "${color}" "${info}"
 	fi
 }
 
 ___brainy_prompt_dir() {
-	color=$bold_yellow
+	color=${bold_yellow?}
 	box="[|]"
 	info="\w"
-	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white}" "${box}"
+	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white?}" "${box}"
 }
 
 ___brainy_prompt_scm() {
 	[ "${THEME_SHOW_SCM}" != "true" ] && return
-	color=$bold_green
+	color=${bold_green?}
 	box="$(scm_char) "
 	info="$(scm_prompt_info)"
-	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white}" "${box}"
+	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white?}" "${box}"
 }
 
 ___brainy_prompt_python() {
 	[ "${THEME_SHOW_PYTHON}" != "true" ] && return
-	color=$bold_yellow
+	color=${bold_yellow?}
 	box="[|]"
 	info="$(python_version_prompt)"
-	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_blue}" "${box}"
+	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_blue?}" "${box}"
 }
 
 ___brainy_prompt_ruby() {
 	[ "${THEME_SHOW_RUBY}" != "true" ] && return
-	color=$bold_white
+	color=${bold_white?}
 	box="[|]"
 	info="rb-$(ruby_version_prompt)"
-	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_red}" "${box}"
+	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_red?}" "${box}"
 }
 
 ___brainy_prompt_todo() {
 	[ "${THEME_SHOW_TODO}" != "true" ] \
 		|| [ -z "$(which todo.sh)" ] && return
-	color=$bold_white
+	color=${bold_white?}
 	box="[|]"
 	info="t:$(todo.sh ls | grep -E "TODO: [0-9]+ of ([0-9]+)" | awk '{ print $4 }')"
-	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_green}" "${box}"
+	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_green?}" "${box}"
 }
 
 ___brainy_prompt_clock() {
@@ -150,7 +150,7 @@ ___brainy_prompt_clock() {
 	color=$THEME_CLOCK_COLOR
 	box="[|]"
 	info="$(date +"${THEME_CLOCK_FORMAT}")"
-	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_purple}" "${box}"
+	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_purple?}" "${box}"
 }
 
 ___brainy_prompt_battery() {
@@ -159,28 +159,28 @@ ___brainy_prompt_battery() {
 		|| [ "$(battery_percentage)" = "no" ] && return
 
 	info=$(battery_percentage)
-	color=$bold_green
+	color=${bold_green?}
 	if [ "$info" -lt 50 ]; then
-		color=$bold_yellow
+		color=${bold_yellow?}
 	elif [ "$info" -lt 25 ]; then
-		color=$bold_red
+		color=${bold_red?}
 	fi
 	box="[|]"
 	ac_adapter_connected && charging="+"
 	ac_adapter_disconnected && charging="-"
 	info+="$charging"
 	[ "$info" == "100+" ] && info="AC"
-	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white}" "${box}"
+	printf "%s|%s|%s|%s" "${color}" "${info}" "${bold_white?}" "${box}"
 }
 
 ___brainy_prompt_exitcode() {
 	[ "${THEME_SHOW_EXITCODE}" != "true" ] && return
-	color=$bold_purple
+	color=${bold_purple?}
 	[ "$exitcode" -ne 0 ] && printf "%s|%s" "${color}" "${exitcode}"
 }
 
 ___brainy_prompt_char() {
-	color=$bold_white
+	color=${bold_white?}
 	prompt_char="${__BRAINY_PROMPT_CHAR_PS1}"
 	printf "%s|%s" "${color}" "${prompt_char}"
 }
@@ -258,8 +258,8 @@ export RVM_THEME_PROMPT_SUFFIX=""
 export VIRTUALENV_THEME_PROMPT_PREFIX=""
 export VIRTUALENV_THEME_PROMPT_SUFFIX=""
 
-export SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-export SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
+export SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+export SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
 
 THEME_SHOW_SUDO=${THEME_SHOW_SUDO:-"true"}
 THEME_SHOW_SCM=${THEME_SHOW_SCM:-"true"}
@@ -270,7 +270,7 @@ THEME_SHOW_TODO=${THEME_SHOW_TODO:-"false"}
 THEME_SHOW_BATTERY=${THEME_SHOW_BATTERY:-"false"}
 THEME_SHOW_EXITCODE=${THEME_SHOW_EXITCODE:-"true"}
 
-THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"$bold_white"}
+THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"${bold_white?}"}
 THEME_CLOCK_FORMAT=${THEME_CLOCK_FORMAT:-"%H:%M:%S"}
 
 __BRAINY_PROMPT_CHAR_PS1=${THEME_PROMPT_CHAR_PS1:-">"}
@@ -285,12 +285,12 @@ ___BRAINY_BOTTOM=${___BRAINY_BOTTOM:-"exitcode char"}
 ############
 
 __brainy_ps1() {
-	printf "%s%s%s" "$(____brainy_top)" "$(____brainy_bottom)" "${normal}"
+	printf "%s%s%s" "$(____brainy_top)" "$(____brainy_bottom)" "${normal?}"
 }
 
 __brainy_ps2() {
-	color=$bold_white
-	printf "%s%s%s" "${color}" "${__BRAINY_PROMPT_CHAR_PS2}  " "${normal}"
+	color=${bold_white?}
+	printf "%s%s%s" "${color}" "${__BRAINY_PROMPT_CHAR_PS2}  " "${normal?}"
 }
 
 _brainy_prompt() {
diff --git a/themes/clean/clean.theme.bash b/themes/clean/clean.theme.bash
index 47a436b34d..55558219b9 100644
--- a/themes/clean/clean.theme.bash
+++ b/themes/clean/clean.theme.bash
@@ -12,13 +12,14 @@ export LSCOLORS="Gxfxcxdxbxegedabagacad"
 export LS_COLORS='no=00:fi=00:di=01;34:ln=00;36:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=41;33;01:ex=00;32:*.cmd=00;32:*.exe=01;32:*.com=01;32:*.bat=01;32:*.btm=01;32:*.dll=01;32:*.tar=00;31:*.tbz=00;31:*.tgz=00;31:*.rpm=00;31:*.deb=00;31:*.arj=00;31:*.taz=00;31:*.lzh=00;31:*.lzma=00;31:*.zip=00;31:*.zoo=00;31:*.z=00;31:*.Z=00;31:*.gz=00;31:*.bz2=00;31:*.tb2=00;31:*.tz2=00;31:*.tbz2=00;31:*.avi=01;35:*.bmp=01;35:*.fli=01;35:*.gif=01;35:*.jpg=01;35:*.jpeg=01;35:*.mng=01;35:*.mov=01;35:*.mpg=01;35:*.pcx=01;35:*.pbm=01;35:*.pgm=01;35:*.png=01;35:*.ppm=01;35:*.tga=01;35:*.tif=01;35:*.xbm=01;35:*.xpm=01;35:*.dl=01;35:*.gl=01;35:*.wmv=01;35:*.aiff=00;32:*.au=00;32:*.mid=00;32:*.mp3=00;32:*.ogg=00;32:*.voc=00;32:*.wav=00;32:'
 
 function prompt_command() {
+	local no_color
 	if [ "$(whoami)" = root ]; then
 		no_color=${red?}
 	else
 		no_color=${white?}
 	fi
 
-	PS1="${no_color}\u${reset_color}:${blue?}\W/${reset_color} $(scm_prompt_info)${normal?}$ "
+	PS1="${no_color}\u${reset_color?}:${blue?}\W/${reset_color?} $(scm_prompt_info)${normal?}$ "
 }
 
 safe_append_prompt_command prompt_command
diff --git a/themes/doubletime/doubletime.theme.bash b/themes/doubletime/doubletime.theme.bash
index e60711aaf0..62881d2334 100644
--- a/themes/doubletime/doubletime.theme.bash
+++ b/themes/doubletime/doubletime.theme.bash
@@ -3,38 +3,38 @@
 
 SCM_THEME_PROMPT_DIRTY=''
 SCM_THEME_PROMPT_CLEAN=''
-SCM_GIT_CHAR="${bold_cyan}±${normal}"
-SCM_SVN_CHAR="${bold_cyan}⑆${normal}"
-SCM_HG_CHAR="${bold_red}☿${normal}"
+SCM_GIT_CHAR="${bold_cyan?}±${normal?}"
+SCM_SVN_CHAR="${bold_cyan?}⑆${normal?}"
+SCM_HG_CHAR="${bold_red?}☿${normal?}"
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 if [[ -n "$RVM_THEME_PROMPT_COLOR" ]]; then
 	RVM_THEME_PROMPT_COLOR=$(eval "echo $$(echo ${RVM_THEME_PROMPT_COLOR})")
 else
-	RVM_THEME_PROMPT_COLOR="${red}"
+	RVM_THEME_PROMPT_COLOR="${red?}"
 fi
-RVM_THEME_PROMPT_PREFIX="(${RVM_THEME_PROMPT_COLOR}rb${normal}: "
+RVM_THEME_PROMPT_PREFIX="(${RVM_THEME_PROMPT_COLOR}rb${normal?}: "
 RVM_THEME_PROMPT_SUFFIX=") "
 if [[ -n "$VIRTUALENV_THEME_PROMPT_COLOR" ]]; then
 	VIRTUALENV_THEME_PROMPT_COLOR=$(eval "echo $$(echo ${VIRTUALENV_THEME_PROMPT_COLOR})")
 else
-	VIRTUALENV_THEME_PROMPT_COLOR="${green}"
+	VIRTUALENV_THEME_PROMPT_COLOR="${green?}"
 fi
-VIRTUALENV_THEME_PROMPT_PREFIX="(${VIRTUALENV_THEME_PROMPT_COLOR}py${normal}: "
+VIRTUALENV_THEME_PROMPT_PREFIX="(${VIRTUALENV_THEME_PROMPT_COLOR}py${normal?}: "
 VIRTUALENV_THEME_PROMPT_SUFFIX=") "
 
 if [[ -n "$THEME_PROMPT_HOST_COLOR" ]]; then
 	THEME_PROMPT_HOST_COLOR=$(eval "echo $$(echo ${THEME_PROMPT_HOST_COLOR})")
 else
-	THEME_PROMPT_HOST_COLOR="$blue"
+	THEME_PROMPT_HOST_COLOR="${blue?}"
 fi
 
 function prompt_setter() {
 	# Save history
 	_save-and-reload-history 1
 	PS1="
-$(clock_prompt) $(scm_char) [${THEME_PROMPT_HOST_COLOR}\u@${THEME_PROMPT_HOST}$reset_color] $(virtualenv_prompt)$(ruby_version_prompt)\w
-$(scm_prompt)$reset_color $ "
+$(clock_prompt) $(scm_char) [${THEME_PROMPT_HOST_COLOR}\u@${THEME_PROMPT_HOST}${reset_color?}] $(virtualenv_prompt)$(ruby_version_prompt)\w
+$(scm_prompt)${reset_color?} $ "
 	PS2='> '
 	PS4='+ '
 }
diff --git a/themes/doubletime_multiline/doubletime_multiline.theme.bash b/themes/doubletime_multiline/doubletime_multiline.theme.bash
index 32e789ea5f..366010436c 100644
--- a/themes/doubletime_multiline/doubletime_multiline.theme.bash
+++ b/themes/doubletime_multiline/doubletime_multiline.theme.bash
@@ -9,7 +9,7 @@ function prompt_setter() {
 	PS1="
 $(clock_prompt) $(scm_char) [$THEME_PROMPT_HOST_COLOR\u@${THEME_PROMPT_HOST}${reset_color?}] $(virtualenv_prompt)$(ruby_version_prompt)
 \w
-$(scm_prompt)$reset_color $ "
+$(scm_prompt)${reset_color?} $ "
 	PS2='> '
 	PS4='+ '
 }
diff --git a/themes/doubletime_multiline_pyonly/doubletime_multiline_pyonly.theme.bash b/themes/doubletime_multiline_pyonly/doubletime_multiline_pyonly.theme.bash
index aa078e788d..2729e7989f 100644
--- a/themes/doubletime_multiline_pyonly/doubletime_multiline_pyonly.theme.bash
+++ b/themes/doubletime_multiline_pyonly/doubletime_multiline_pyonly.theme.bash
@@ -9,7 +9,7 @@ function prompt_setter() {
 	PS1="
 $(clock_prompt) $(scm_char) [$THEME_PROMPT_HOST_COLOR\u@${THEME_PROMPT_HOST}${reset_color?}] $(virtualenv_prompt)
 \w
-$(scm_prompt)$reset_color $ "
+$(scm_prompt)${reset_color?} $ "
 	PS2='> '
 	PS4='+ '
 }
diff --git a/themes/dulcie/dulcie.theme.bash b/themes/dulcie/dulcie.theme.bash
index be08940344..27e5a19190 100644
--- a/themes/dulcie/dulcie.theme.bash
+++ b/themes/dulcie/dulcie.theme.bash
@@ -54,11 +54,11 @@ dulcie_prompt() {
 		DULCIE_WORKINGDIR="${color_workingdir?}\W${reset_color?}"
 		DULCIE_PROMPTCHAR="${color_user?}"'\$'"${reset_color?}"
 
-		SCM_THEME_PROMPT_DIRTY=" ${red?}✗${reset_color}"
+		SCM_THEME_PROMPT_DIRTY=" ${red?}✗${reset_color?}"
 		SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
 		DULCIE_SCM_BACKGROUND="${background_scm}"
 		DULCIE_SCM_DIR_COLOR="${color_rootdir}"
-		SCM_THEME_ROOT_SUFFIX="${reset_color}${SCM_THEME_ROOT_SUFFIX}"
+		SCM_THEME_ROOT_SUFFIX="${reset_color?}${SCM_THEME_ROOT_SUFFIX}"
 		SCM_THEME_PROMPT_DIRTY=" $(dulcie_color 1)✗${reset_color?}"
 		SCM_THEME_PROMPT_CLEAN=" $(dulcie_color 10)✓${reset_color?}"
 	else
@@ -80,17 +80,17 @@ dulcie_prompt() {
 	# Open the new terminal in the same directory
 	_is_function __vte_osc7 && __vte_osc7
 
-	PS1="${reset_color}[${DULCIE_USER}@${DULCIE_HOST}$(scm_prompt_info)${reset_color?} ${DULCIE_WORKINGDIR}]"
+	PS1="${reset_color?}[${DULCIE_USER}@${DULCIE_HOST}$(scm_prompt_info)${reset_color?} ${DULCIE_WORKINGDIR}]"
 	if [[ "${DULCIE_MULTILINE}" -eq "1" ]]; then
-		PS1="${reset_color}[${DULCIE_USER}@${DULCIE_HOST}${reset_color?} ${DULCIE_WORKINGDIR}]"
+		PS1="${reset_color?}[${DULCIE_USER}@${DULCIE_HOST}${reset_color?} ${DULCIE_WORKINGDIR}]"
 		if [[ "$(scm_prompt_info)" ]]; then
 			SCM_THEME_PROMPT_PREFIX="${DULCIE_SCM_BACKGROUND}|${DULCIE_SCM_DIR_COLOR}"
-			SCM_THEME_PROMPT_SUFFIX="|${normal}"
+			SCM_THEME_PROMPT_SUFFIX="|${normal?}"
 			PS1="$(scm_prompt_info)\n${PS1}"
 		fi
 	else
 		SCM_THEME_PROMPT_PREFIX=" ${DULCIE_SCM_BACKGROUND}|${DULCIE_SCM_DIR_COLOR}"
-		SCM_THEME_PROMPT_SUFFIX="|${normal}"
+		SCM_THEME_PROMPT_SUFFIX="|${normal?}"
 		PS1="${reset_color?}[${DULCIE_USER}@${DULCIE_HOST}$(scm_prompt_info)${reset_color?} ${DULCIE_WORKINGDIR}]"
 	fi
 	PS1="${PS1}${DULCIE_PROMPTCHAR} "
diff --git a/themes/elixr/elixr.theme.bash b/themes/elixr/elixr.theme.bash
index d266fae89d..62dd435554 100644
--- a/themes/elixr/elixr.theme.bash
+++ b/themes/elixr/elixr.theme.bash
@@ -18,7 +18,7 @@ RVM_THEME_PROMPT_SUFFIX=" d|"
 BOLD="\[\e[1m\]"
 
 function prompt_command() {
-	PS1="\n${bold_cyan?}$(scm_prompt_char_info)$(virtualenv_prompt) ${bold_cyan}\w :${reset_color?}${normal?}${BOLD} "
+	PS1="\n${bold_cyan?}$(scm_prompt_char_info)$(virtualenv_prompt) ${bold_cyan?}\w :${reset_color?}${normal?}${BOLD} "
 }
 
 safe_append_prompt_command prompt_command
diff --git a/themes/inretio/inretio.theme.bash b/themes/inretio/inretio.theme.bash
index 1db6c6d1f4..9f640bf8af 100644
--- a/themes/inretio/inretio.theme.bash
+++ b/themes/inretio/inretio.theme.bash
@@ -84,15 +84,15 @@ _theme_clock() {
 	fi
 }
 THEME_SHOW_CLOCK_CHAR=${THEME_SHOW_CLOCK_CHAR:-"false"}
-THEME_CLOCK_CHAR_COLOR=${THEME_CLOCK_CHAR_COLOR:-"$red"}
-THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"$normal"}
+THEME_CLOCK_CHAR_COLOR=${THEME_CLOCK_CHAR_COLOR:-"${red?}"}
+THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"${normal?}"}
 THEME_CLOCK_FORMAT=${THEME_CLOCK_FORMAT:-"%Y-%m-%d %H:%M:%S"}
 
 # PROMPT OUTPUT ===============================================================
 
 # Displays the current prompt
 function prompt_command() {
-	PS1="\n${icon_start}$(_theme_clock)${icon_user}${bold_green?}\u${normal}${icon_host}${bold_cyan?}\h${normal}${green?}$(_virtualenv_prompt)${normal}${icon_directory}${bold_purple?}\W${normal}\$([[ -n \$(git branch 2> /dev/null) ]] && echo \" on ${icon_branch} $(scm_prompt_info) \")${white?}${normal}\n${icon_end}"
+	PS1="\n${icon_start}$(_theme_clock)${icon_user}${bold_green?}\u${normal?}${icon_host}${bold_cyan?}\h${normal?}${green?}$(_virtualenv_prompt)${normal?}${icon_directory}${bold_purple?}\W${normal?}\$([[ -n \$(git branch 2> /dev/null) ]] && echo \" on ${icon_branch} $(scm_prompt_info) \")${white?}${normal}\n${icon_end}"
 	PS2="${icon_end}"
 }
 
diff --git a/themes/lambda/lambda.theme.bash b/themes/lambda/lambda.theme.bash
index 59f82a4a81..20d118e297 100644
--- a/themes/lambda/lambda.theme.bash
+++ b/themes/lambda/lambda.theme.bash
@@ -23,13 +23,13 @@ function set_prompt {
 	PS1+="${dir_color} \\w"             # current working directory
 
 	# Git information (status symbol)
-	PS1+=" ${git_color}$(__git_ps1 "[%s]")${reset_color}"
+	PS1+=" ${git_color}$(__git_ps1 "[%s]")${reset_color?}"
 
 	if [ $time_taken -gt 0 ]; then
 		PS1+=" ${time_color}took ${time_taken}ms" # time taken in milliseconds
 	fi
 
-	PS1+="\n${prompt_symbol_color}╰─λ${reset_color} " # red color for the prompt symbol, reset color after
+	PS1+="\n${prompt_symbol_color}╰─λ${reset_color?} " # red color for the prompt symbol, reset color after
 }
 
 PROMPT_COMMAND='start_time=$(date +%s%3N); set_prompt'
diff --git a/themes/mairan/mairan.theme.bash b/themes/mairan/mairan.theme.bash
index 65ef7ac1d3..66c526913c 100644
--- a/themes/mairan/mairan.theme.bash
+++ b/themes/mairan/mairan.theme.bash
@@ -1,3 +1,6 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # Mairan Bash Prompt, inspired by "Zork"
 
 if tput setaf 1 &> /dev/null; then
@@ -34,11 +37,11 @@ BRACKET_COLOR=$ORANGE
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
-SCM_GIT_CHAR="${bold_green}±${normal}"
-SCM_SVN_CHAR="${bold_cyan}⑆${normal}"
-SCM_HG_CHAR="${bold_red}☿${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
+SCM_GIT_CHAR="${bold_green?}±${normal?}"
+SCM_SVN_CHAR="${bold_cyan?}⑆${normal?}"
+SCM_HG_CHAR="${bold_red?}☿${normal?}"
 
 #Mysql Prompt
 export MYSQL_PS1="(\u@\h) [\d]> "
@@ -55,58 +58,61 @@ esac
 PS3=">> "
 
 __my_rvm_ruby_version() {
-	local gemset=$(echo $GEM_HOME | awk -F'@' '{print $2}')
-	[ "$gemset" != "" ] && gemset="@$gemset"
-	local version=$(echo $MY_RUBY_HOME | awk -F'-' '{print $2}')
-	local full="$version$gemset"
-	[ "$full" != "" ] && echo "[$full]"
+	local version gemset
+	gemset=$(echo "${GEM_HOME}" | awk -F'@' '{print $2}')
+	[[ -n "${gemset}" ]] && gemset="@${gemset}"
+	version=$(echo "${MY_RUBY_HOME}" | awk -F'-' '{print $2}')
+	local full="${version}${gemset}"
+	[[ -n "${full}" ]] && echo "[${full}]"
 }
 
 is_vim_shell() {
-	if [ ! -z "$VIMRUNTIME" ]; then
-		echo "[${cyan}vim shell${normal}]"
+	if [[ -n "$VIMRUNTIME" ]]; then
+		echo "[${cyan?}vim shell${normal?}]"
 	fi
 }
 
 # show chroot if exist
 chroot() {
-	if [ -n "$debian_chroot" ]; then
-		my_ps_chroot="${bold_cyan}$debian_chroot${normal}"
+	if [[ -n "$debian_chroot" ]]; then
+		my_ps_chroot="${bold_cyan?}$debian_chroot${normal?}"
 		echo "($my_ps_chroot)"
 	fi
 }
 
 # show virtualenvwrapper
 my_ve() {
-	if [ -n "$VIRTUAL_ENV" ]; then
-		my_ps_ve="${bold_purple}$ve${normal}"
+	if [[ -n "$VIRTUAL_ENV" ]]; then
+		my_ps_ve="${bold_purple?}$ve${normal?}"
 		echo "($my_ps_ve)"
 	fi
 	echo ""
 }
 
 prompt() {
-	SCM_PROMPT_FORMAT="[%s$GREEN%s]"
-	my_ps_host="$BOLD$ORANGE\h${normal}"
+	SCM_PROMPT_FORMAT="[%s${GREEN}%s]"
+	my_ps_host="${BOLD}${ORANGE}\h${normal?}"
 	# yes, these are the the same for now ...
-	my_ps_host_root="$ORANGE\h${normal}"
+	my_ps_host_root="${ORANGE}\h${normal?}"
 
-	my_ps_user="$BOLD$GREEN\u${normal}"
-	my_ps_root="${bold_red}\u${normal}"
+	my_ps_user="${BOLD}${GREEN}\u${normal?}"
+	my_ps_root="${bold_red?}\u${normal?}"
 
-	if [ -n "$VIRTUAL_ENV" ]; then
-		ve=$(basename "$VIRTUAL_ENV")
+	if [[ -n "$VIRTUAL_ENV" ]]; then
+		ve=$(basename "${VIRTUAL_ENV}")
 	fi
 
 	# nice prompt
 	case "$(id -u)" in
 		0)
-			PS1="\n${TITLEBAR}${BRACKET_COLOR}┌─${normal}$(my_ve)$(chroot)[$my_ps_root][$my_ps_host_root]$(scm_prompt)$(__my_rvm_ruby_version)[${green}\w${normal}]$(is_vim_shell)${BRACKET_COLOR}
-└─▪ ${prompt_symbol} ${normal}"
+			# shellcheck disable=SC2312
+			PS1="\n${TITLEBAR}${BRACKET_COLOR}┌─${normal?}$(my_ve)$(chroot)[$my_ps_root][$my_ps_host_root]$(scm_prompt)$(__my_rvm_ruby_version)[${green?}\w${normal?}]$(is_vim_shell)${BRACKET_COLOR}
+└─▪ ${prompt_symbol} ${normal?}"
 			;;
 		*)
-			PS1="\n${TITLEBAR}${BRACKET_COLOR}┌─${normal}$(my_ve)$(chroot)[$my_ps_user][$my_ps_host]$(scm_prompt)${normal}$(__my_rvm_ruby_version)[${green}\w${normal}]$(is_vim_shell)${BRACKET_COLOR}
-└─▪ ${prompt_symbol} ${normal}"
+			# shellcheck disable=SC2312
+			PS1="\n${TITLEBAR}${BRACKET_COLOR}┌─${normal?}$(my_ve)$(chroot)[$my_ps_user][$my_ps_host]$(scm_prompt)${normal?}$(__my_rvm_ruby_version)[${green?}\w${normal?}]$(is_vim_shell)${BRACKET_COLOR}
+└─▪ ${prompt_symbol} ${normal?}"
 			;;
 	esac
 }
diff --git a/themes/mbriggs/mbriggs.theme.bash b/themes/mbriggs/mbriggs.theme.bash
index 9e1511e316..d6071d93c2 100644
--- a/themes/mbriggs/mbriggs.theme.bash
+++ b/themes/mbriggs/mbriggs.theme.bash
@@ -1,16 +1,19 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # ------------------------------------------------------------------#
 #          FILE: mbriggs.zsh-theme                                  #
 #            BY: Matt Briggs (matt@mattbriggs.net)                  #
 #      BASED ON: smt by Stephen Tudor (stephen@tudorstudio.com)     #
 # ------------------------------------------------------------------#
 
-SCM_THEME_PROMPT_DIRTY="${red}⚡${reset_color}"
-SCM_THEME_PROMPT_AHEAD="${red}!${reset_color}"
-SCM_THEME_PROMPT_CLEAN="${green}✓${reset_color}"
+SCM_THEME_PROMPT_DIRTY="${red?}⚡${reset_color?}"
+SCM_THEME_PROMPT_AHEAD="${red?}!${reset_color?}"
+SCM_THEME_PROMPT_CLEAN="${green?}✓${reset_color?}"
 SCM_THEME_PROMPT_PREFIX=" "
 SCM_THEME_PROMPT_SUFFIX=""
-GIT_SHA_PREFIX=" ${yellow}"
-GIT_SHA_SUFFIX="${reset_color}"
+GIT_SHA_PREFIX=" ${yellow?}"
+GIT_SHA_SUFFIX="${reset_color?}"
 
 function git_short_sha() {
 	SHA=$(git rev-parse --short HEAD 2> /dev/null) && echo "$GIT_SHA_PREFIX$SHA$GIT_SHA_SUFFIX"
@@ -18,11 +21,13 @@ function git_short_sha() {
 
 function prompt() {
 	local return_status=""
-	local ruby="${red}$(ruby_version_prompt)${reset_color}"
-	local user_host="${green}\h${reset_color}"
+	local ruby
+	ruby="${red?}$(ruby_version_prompt)${reset_color?}"
+	local user_host="${green?}\h${reset_color?}"
 	local current_path="\w"
 	local n_commands="\!"
-	local git_branch="$(git_short_sha)$(scm_prompt_info)"
+	local git_branch
+	git_branch="$(git_short_sha)$(scm_prompt_info)"
 	local prompt_symbol='λ'
 	local open='('
 	local close=')'
diff --git a/themes/metal/metal.theme.bash b/themes/metal/metal.theme.bash
index e68a90a9b7..676bb497c1 100644
--- a/themes/metal/metal.theme.bash
+++ b/themes/metal/metal.theme.bash
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 # Emoji-based theme to display source control management and
 # virtual environment info beside the ordinary bash prompt.
@@ -21,11 +22,11 @@ VIRTUALENV_THEME_PROMPT_SUFFIX=""
 # SCM prompts
 SCM_NONE_CHAR=""
 SCM_GIT_CHAR="[±] "
-SCM_GIT_BEHIND_CHAR="${red}↓${normal}"
-SCM_GIT_AHEAD_CHAR="${bold_green}↑${normal}"
+SCM_GIT_BEHIND_CHAR="${red?}↓${normal?}"
+SCM_GIT_AHEAD_CHAR="${bold_green?}↑${normal?}"
 SCM_GIT_UNTRACKED_CHAR="⌀"
-SCM_GIT_UNSTAGED_CHAR="${bold_yellow}•${normal}"
-SCM_GIT_STAGED_CHAR="${bold_green}+${normal}"
+SCM_GIT_UNSTAGED_CHAR="${bold_yellow?}•${normal?}"
+SCM_GIT_STAGED_CHAR="${bold_green?}+${normal?}"
 
 SCM_THEME_PROMPT_DIRTY=""
 SCM_THEME_PROMPT_CLEAN=""
@@ -33,8 +34,8 @@ SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 
 # Git status prompts
-GIT_THEME_PROMPT_DIRTY=" ${red}✗${normal}"
-GIT_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
+GIT_THEME_PROMPT_DIRTY=" ${red?}✗${normal?}"
+GIT_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
 GIT_THEME_PROMPT_PREFIX=""
 GIT_THEME_PROMPT_SUFFIX=""
 
@@ -61,11 +62,13 @@ function virtualenv_prompt {
 
 # Rename tab
 function tabname {
+	# shellcheck disable=SC2059
 	printf "\e]1;$1\a"
 }
 
 # Rename window
 function winname {
+	# shellcheck disable=SC2059
 	printf "\e]2;$1\a"
 }
 
@@ -73,7 +76,7 @@ function winname {
 
 # Displays the current prompt
 function prompt_command() {
-	PS1="\n${icon_start}$(virtualenv_prompt)${icon_user}${bold_green}\u${normal}${icon_host}${bold_cyan}\h${normal}${icon_directory}${bold_purple}\W${normal}\$([[ -n \$(git branch 2> /dev/null) ]] && echo \" on ${icon_branch}  \")${white}$(scm_prompt_info)${normal}\n${icon_end}"
+	PS1="\n${icon_start}$(virtualenv_prompt)${icon_user}${bold_green?}\u${normal?}${icon_host}${bold_cyan?}\h${normal?}${icon_directory}${bold_purple?}\W${normal?}\$([[ -n \$(git branch 2> /dev/null) ]] && echo \" on ${icon_branch}  \")${white?}$(scm_prompt_info)${normal?}\n${icon_end}"
 	PS2="${icon_end}"
 }
 
diff --git a/themes/minimal/minimal.theme.bash b/themes/minimal/minimal.theme.bash
index 2bf807c16f..52490735f4 100644
--- a/themes/minimal/minimal.theme.bash
+++ b/themes/minimal/minimal.theme.bash
@@ -1,12 +1,13 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
-SCM_THEME_PROMPT_PREFIX="${cyan}(${green}"
-SCM_THEME_PROMPT_SUFFIX="${cyan})"
-SCM_THEME_PROMPT_DIRTY=" ${red}✗"
-SCM_THEME_PROMPT_CLEAN=" ${green}✓"
+SCM_THEME_PROMPT_PREFIX="${cyan?}(${green?}"
+SCM_THEME_PROMPT_SUFFIX="${cyan?})"
+SCM_THEME_PROMPT_DIRTY=" ${red?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${green?}✓"
 
 prompt() {
-	PS1="$(scm_prompt_info)${reset_color} ${cyan}\W${reset_color} "
+	PS1="$(scm_prompt_info)${reset_color?} ${cyan?}\W${reset_color?} "
 }
 
 safe_append_prompt_command prompt
diff --git a/themes/modern-t/modern-t.theme.bash b/themes/modern-t/modern-t.theme.bash
index c0a5b556e7..eed15a94de 100644
--- a/themes/modern-t/modern-t.theme.bash
+++ b/themes/modern-t/modern-t.theme.bash
@@ -1,3 +1,6 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # The "modern-t" theme is a "modern" theme variant with support
 # for "t", the minimalist python todo list utility by Steve Losh.
 # Get and install "t" at https://github.com/sjl/t#installing-t
@@ -8,11 +11,11 @@
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
-SCM_GIT_CHAR="${bold_green}±${normal}"
-SCM_SVN_CHAR="${bold_cyan}⑆${normal}"
-SCM_HG_CHAR="${bold_red}☿${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
+SCM_GIT_CHAR="${bold_green?}±${normal?}"
+SCM_SVN_CHAR="${bold_cyan?}⑆${normal?}"
+SCM_HG_CHAR="${bold_red?}☿${normal?}"
 
 case $TERM in
 	xterm*)
@@ -27,20 +30,21 @@ PS3=">> "
 
 is_vim_shell() {
 	if [ ! -z "$VIMRUNTIME" ]; then
-		echo "[${cyan}vim shell${normal}]"
+		echo "[${cyan?}vim shell${normal?}]"
 	fi
 }
 
 prompt() {
 	SCM_PROMPT_FORMAT='[%s][%s]'
-	if [ $? -ne 0 ]; then
+	# shellcheck disable=SC2181 # How can this assignment fail? an immutable VAR name?
+	if [[ $? -ne 0 ]]; then
 		# Yes, the indenting on these is weird, but it has to be like
 		# this otherwise it won't display properly.
 
-		PS1="${TITLEBAR}${bold_red}┌─[${cyan}$(t | wc -l | sed -e's/ *//')${reset_color}]${reset_color}$(scm_prompt)[${cyan}\W${normal}]$(is_vim_shell)
-${bold_red}└─▪${normal} "
+		PS1="${TITLEBAR}${bold_red?}┌─[${cyan?}$(t | wc -l | sed -e's/ *//')${reset_color?}]${reset_color?}$(scm_prompt)[${cyan?}\W${normal?}]$(is_vim_shell)
+${bold_red?}└─▪${normal?} "
 	else
-		PS1="${TITLEBAR}┌─[${cyan}$(t | wc -l | sed -e's/ *//')${reset_color}]$(scm_prompt)[${cyan}\W${normal}]$(is_vim_shell)
+		PS1="${TITLEBAR}┌─[${cyan?}$(t | wc -l | sed -e's/ *//')${reset_color?}]$(scm_prompt)[${cyan?}\W${normal?}]$(is_vim_shell)
 └─▪ "
 	fi
 }
diff --git a/themes/modern-time/modern-time.theme.bash b/themes/modern-time/modern-time.theme.bash
index ceb2f5ede3..2ae39552ee 100644
--- a/themes/modern-time/modern-time.theme.bash
+++ b/themes/modern-time/modern-time.theme.bash
@@ -1,16 +1,19 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # Modified version of the original modern theme in bash-it
 # Removes the battery charge and adds the current time
 
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
-SCM_GIT_CHAR="${bold_green}±${normal}"
-SCM_SVN_CHAR="${bold_cyan}⑆${normal}"
-SCM_HG_CHAR="${bold_red}☿${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
+SCM_GIT_CHAR="${bold_green?}±${normal?}"
+SCM_SVN_CHAR="${bold_cyan?}⑆${normal?}"
+SCM_HG_CHAR="${bold_red?}☿${normal?}"
 
-case $TERM in
+case ${TERM} in
 	xterm*)
 		TITLEBAR="\[\033]0;\w\007\]"
 		;;
@@ -22,8 +25,8 @@ esac
 PS3=">> "
 
 is_vim_shell() {
-	if [ ! -z "$VIMRUNTIME" ]; then
-		echo "[${cyan}vim shell${normal}]"
+	if [[ -n "$VIMRUNTIME" ]]; then
+		echo "[${cyan?}vim shell${normal?}]"
 	fi
 }
 
@@ -32,15 +35,16 @@ modern_current_time_prompt() {
 }
 
 prompt() {
-	SCM_PROMPT_FORMAT='[%s][%s]'
 	if [ $? -ne 0 ]; then
+		SCM_PROMPT_FORMAT='[%s][%s]'
 		# Yes, the indenting on these is weird, but it has to be like
 		# this otherwise it won't display properly.
 
-		PS1="${TITLEBAR}${bold_red}┌─${reset_color}$(scm_prompt)$(modern_current_time_prompt)[${cyan}\W${normal}]$(is_vim_shell)
-${bold_red}└─▪${normal} "
+		PS1="${TITLEBAR}${bold_red?}┌─${reset_color?}$(scm_prompt)$(modern_current_time_prompt)[${cyan?}\W${normal?}]$(is_vim_shell)
+${bold_red?}└─▪${normal?} "
 	else
-		PS1="${TITLEBAR}┌─$(scm_prompt)$(modern_current_time_prompt)[${cyan}\W${normal}]$(is_vim_shell)
+		SCM_PROMPT_FORMAT='[%s][%s]'
+		PS1="${TITLEBAR}┌─$(scm_prompt)$(modern_current_time_prompt)[${cyan?}\W${normal?}]$(is_vim_shell)
 └─▪ "
 	fi
 }
diff --git a/themes/morris/morris.theme.bash b/themes/morris/morris.theme.bash
index 58b1bad816..d23eea63e4 100644
--- a/themes/morris/morris.theme.bash
+++ b/themes/morris/morris.theme.bash
@@ -1,3 +1,6 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # prompt theming
 
 # added TITLEBAR for updating the tab and window titles with the pwd
@@ -18,9 +21,9 @@ function prompt_command() {
 }
 
 # scm theming
-SCM_THEME_PROMPT_DIRTY=" ${red}✗"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓"
-SCM_THEME_PROMPT_PREFIX="${green}("
-SCM_THEME_PROMPT_SUFFIX="${green})${reset_color}"
+SCM_THEME_PROMPT_DIRTY=" ${red?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓"
+SCM_THEME_PROMPT_PREFIX="${green?}("
+SCM_THEME_PROMPT_SUFFIX="${green?})${reset_color?}"
 
 safe_append_prompt_command prompt_command
diff --git a/themes/n0qorg/n0qorg.theme.bash b/themes/n0qorg/n0qorg.theme.bash
index b82a17f3d4..aaf781acde 100644
--- a/themes/n0qorg/n0qorg.theme.bash
+++ b/themes/n0qorg/n0qorg.theme.bash
@@ -1,4 +1,6 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # n0qorg theme by Florian Baumann <flo@noqqe.de>
 
 ## look-a-like
@@ -6,17 +8,17 @@
 # for example:
 # ananas ~/Code/bash-it/themes (master*)»
 function prompt_command() {
-	PS1="${bold_blue}[$(hostname)]${normal} \w${normal} ${bold_white}[$(git_prompt_info)]${normal}» "
+	PS1="${bold_blue?}[$(hostname)]${normal?} \w${normal?} ${bold_white?}[$(git_prompt_info)]${normal?}» "
 }
 
 safe_append_prompt_command prompt_command
 
 ## git-theme
 # feel free to change git chars.
-GIT_THEME_PROMPT_DIRTY="${bold_blue}*${bold_white}"
+GIT_THEME_PROMPT_DIRTY="${bold_blue?}*${bold_white?}"
 GIT_THEME_PROMPT_CLEAN=""
-GIT_THEME_PROMPT_PREFIX="${bold_blue}(${bold_white}"
-GIT_THEME_PROMPT_SUFFIX="${bold_blue})"
+GIT_THEME_PROMPT_PREFIX="${bold_blue?}(${bold_white?}"
+GIT_THEME_PROMPT_SUFFIX="${bold_blue?})"
 
 ## alternate chars
 #
diff --git a/themes/newin/newin.theme.bash b/themes/newin/newin.theme.bash
index cabd024fe1..1ceed19008 100644
--- a/themes/newin/newin.theme.bash
+++ b/themes/newin/newin.theme.bash
@@ -1,13 +1,14 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
-SCM_THEME_PROMPT_DIRTY=" ${red}✗"
-SCM_THEME_PROMPT_CLEAN=" ${green}✓"
-SCM_THEME_PROMPT_PREFIX=" ${purple}|${green} "
-SCM_THEME_PROMPT_SUFFIX="${purple} |"
+SCM_THEME_PROMPT_DIRTY=" ${red?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${green?}✓"
+SCM_THEME_PROMPT_PREFIX=" ${purple?}|${green?} "
+SCM_THEME_PROMPT_SUFFIX="${purple?} |"
 
 prompt() {
 	exit_code=$?
-	PS1="$(if [[ ${exit_code} = 0 ]]; then echo "${green}${exit_code}"; else echo "${red}${exit_code}"; fi) ${yellow}\t ${cyan}\w$(scm_prompt_info)${reset_color}\n${orange}$ ${reset_color}"
+	PS1="$(if [[ ${exit_code} = 0 ]]; then echo "${green?}${exit_code}"; else echo "${red?}${exit_code}"; fi) ${yellow?}\t ${cyan?}\w$(scm_prompt_info)${reset_color?}\n${orange?}$ ${reset_color?}"
 }
 
 safe_append_prompt_command prompt
diff --git a/themes/nwinkler/nwinkler.theme.bash b/themes/nwinkler/nwinkler.theme.bash
index 5bb66aee69..18d6e018cb 100644
--- a/themes/nwinkler/nwinkler.theme.bash
+++ b/themes/nwinkler/nwinkler.theme.bash
@@ -1,4 +1,5 @@
 # shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 # Two line prompt showing the following information:
 # (time) SCM [username@hostname] pwd (SCM branch SCM status)
@@ -15,8 +16,8 @@
 # The exit code functionality currently doesn't work if you are using the 'fasd' plugin,
 # since 'fasd' is messing with the $PROMPT_COMMAND
 
-PROMPT_END_CLEAN="${green}→${reset_color}"
-PROMPT_END_DIRTY="${red}→${reset_color}"
+PROMPT_END_CLEAN="${green?}→${reset_color?}"
+PROMPT_END_DIRTY="${red?}→${reset_color?}"
 
 function prompt_end() {
 	echo -e "$PROMPT_END"
@@ -31,15 +32,15 @@ prompt_setter() {
 	fi
 	# Save history
 	_save-and-reload-history 1
-	PS1="($(clock_prompt)) $(scm_char) [${blue}\u${reset_color}@${green}\H${reset_color}] ${yellow}\w${reset_color}$(scm_prompt_info) ${reset_color}\n$(prompt_end) "
+	PS1="($(clock_prompt)) $(scm_char) [${blue?}\u${reset_color?}@${green?}\H${reset_color?}] ${yellow?}\w${reset_color?}$(scm_prompt_info) ${reset_color?}\n$(prompt_end) "
 	PS2='> '
 	PS4='+ '
 }
 
 safe_append_prompt_command prompt_setter
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
 SCM_THEME_PROMPT_PREFIX=" ("
 SCM_THEME_PROMPT_SUFFIX=")"
 RVM_THEME_PROMPT_PREFIX=" ("
diff --git a/themes/nwinkler_random_colors/nwinkler_random_colors.theme.bash b/themes/nwinkler_random_colors/nwinkler_random_colors.theme.bash
index c23860a1b4..8862400fd8 100644
--- a/themes/nwinkler_random_colors/nwinkler_random_colors.theme.bash
+++ b/themes/nwinkler_random_colors/nwinkler_random_colors.theme.bash
@@ -1,4 +1,5 @@
 # shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 # Two line prompt showing the following information:
 # (time) SCM [username@hostname] pwd (SCM branch SCM status)
@@ -20,25 +21,26 @@ RANDOM_COLOR_FILE=$HOME/.nwinkler_random_colors
 function randomize_nwinkler {
 	declare -a AVAILABLE_COLORS
 
+	# shellcheck disable=SC2206 # Expected behavior but fine for this theme.
 	AVAILABLE_COLORS=(
-		$black
-		$red
-		$green
-		$yellow
-		$blue
-		$purple
-		$cyan
-		$white
-		$orange
-		$bold_black
-		$bold_red
-		$bold_green
-		$bold_yellow
-		$bold_blue
-		$bold_purple
-		$bold_cyan
-		$bold_white
-		$bold_orange
+		"${black?}"
+		"${red?}"
+		"${green?}"
+		"${yellow?}"
+		"${blue?}"
+		"${purple?}"
+		"${cyan?}"
+		"${white?}"
+		"${orange?}"
+		"${bold_black?}"
+		"${bold_red?}"
+		"${bold_green?}"
+		"${bold_yellow?}"
+		"${bold_blue?}"
+		"${bold_purple?}"
+		"${bold_cyan?}"
+		"${bold_white?}"
+		"${bold_orange?}"
 	)
 	# Uncomment these to allow underlines:
 	#$underline_black
@@ -58,12 +60,12 @@ function randomize_nwinkler {
 	THEME_CLOCK_COLOR=$TIME_COLOR
 	PATH_COLOR=${AVAILABLE_COLORS[$RANDOM % ${#AVAILABLE_COLORS[@]}]}
 
-	echo "$USERNAME_COLOR,$HOSTNAME_COLOR,$TIME_COLOR,$PATH_COLOR," > $RANDOM_COLOR_FILE
+	echo "$USERNAME_COLOR,$HOSTNAME_COLOR,$TIME_COLOR,$PATH_COLOR," > "$RANDOM_COLOR_FILE"
 }
 
-if [ -f $RANDOM_COLOR_FILE ]; then
+if [ -f "$RANDOM_COLOR_FILE" ]; then
 	# read the colors already stored in the file
-	IFS=',' read -ra COLORS < $RANDOM_COLOR_FILE
+	IFS=',' read -ra COLORS < "$RANDOM_COLOR_FILE"
 	USERNAME_COLOR=${COLORS[0]}
 	HOSTNAME_COLOR=${COLORS[1]}
 	TIME_COLOR=${COLORS[2]}
@@ -82,8 +84,8 @@ else
 	echo
 fi
 
-PROMPT_END_CLEAN="${green}→${reset_color}"
-PROMPT_END_DIRTY="${red}→${reset_color}"
+PROMPT_END_CLEAN="${green?}→${reset_color?}"
+PROMPT_END_DIRTY="${red?}→${reset_color?}"
 
 function prompt_end() {
 	echo -e "$PROMPT_END"
@@ -98,15 +100,15 @@ prompt_setter() {
 	fi
 	# Save history
 	_save-and-reload-history 1
-	PS1="($(clock_prompt)${reset_color}) $(scm_char) [${USERNAME_COLOR}\u${reset_color}@${HOSTNAME_COLOR}\H${reset_color}] ${PATH_COLOR}\w${reset_color}$(scm_prompt_info) ${reset_color}\n$(prompt_end) "
+	PS1="($(clock_prompt)${reset_color?}) $(scm_char) [${USERNAME_COLOR}\u${reset_color?}@${HOSTNAME_COLOR}\H${reset_color?}] ${PATH_COLOR}\w${reset_color?}$(scm_prompt_info) ${reset_color}\n$(prompt_end) "
 	PS2='> '
 	PS4='+ '
 }
 
 safe_append_prompt_command prompt_setter
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
 SCM_THEME_PROMPT_PREFIX=" ("
 SCM_THEME_PROMPT_SUFFIX=")"
 RVM_THEME_PROMPT_PREFIX=" ("
diff --git a/themes/oh-my-posh/oh-my-posh.theme.bash b/themes/oh-my-posh/oh-my-posh.theme.bash
index 430c8acb4c..f41615dc6e 100644
--- a/themes/oh-my-posh/oh-my-posh.theme.bash
+++ b/themes/oh-my-posh/oh-my-posh.theme.bash
@@ -1,4 +1,5 @@
 # shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 if _command_exists oh-my-posh; then
 	export POSH_THEME=${POSH_THEME:-https://raw.githubusercontent.com/JanDeDobbeleer/oh-my-posh/v$(oh-my-posh --version)/themes/jandedobbeleer.omp.json}
diff --git a/themes/parrot/parrot.theme.bash b/themes/parrot/parrot.theme.bash
index 266fe8a683..0afd3522d2 100644
--- a/themes/parrot/parrot.theme.bash
+++ b/themes/parrot/parrot.theme.bash
@@ -1,3 +1,6 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # git branch parser
 function parse_git_branch() {
 	echo -e "\[\033[1;34m\]$(git branch 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/(\1)/')\[\033[0m\]"
@@ -25,6 +28,7 @@ function prompt() {
 	fi
 
 	if [ "$color_prompt" = yes ]; then
+		# shellcheck disable=SC2028
 		PS1="\[\033[0;31m\]\342\224\214\342\224\200\$([[ \$? != 0 ]] && echo \"[\[\033[0;31m\]\342\234\227\[\033[0;37m\]]\342\224\200\")[$(if [[ ${EUID} == 0 ]]; then echo '\[\033[01;31m\]root\[\033[01;33m\]@\[\033[01;96m\]\h'; else echo '\[\033[0;39m\]\u\[\033[01;33m\]@\[\033[01;96m\]\h'; fi)\[\033[0;31m\]]\342\224\200[\[\033[0;32m\]\w\[\033[0;31m\]]\n\[\033[0;31m\]\342\224\224\342\224\200\342\224\200\342\225\274 \[\033[0m\]\[\e[01;33m\]$(parse_git_branch) $\[\e[0m\] "
 
 	else
diff --git a/themes/powerline-multiline/powerline-multiline.base.bash b/themes/powerline-multiline/powerline-multiline.base.bash
index 02bbf39eb8..2d3837172b 100644
--- a/themes/powerline-multiline/powerline-multiline.base.bash
+++ b/themes/powerline-multiline/powerline-multiline.base.bash
@@ -22,7 +22,7 @@ function __powerline_right_segment() {
 		# Since the previous segment wasn't the last segment, add padding, if needed
 		#
 		if [[ "${POWERLINE_COMPACT_AFTER_SEPARATOR:-0}" -eq 0 ]]; then
-			RIGHT_PROMPT+="$(set_color - "${LAST_SEGMENT_COLOR?}") ${normal}"
+			RIGHT_PROMPT+="$(set_color - "${LAST_SEGMENT_COLOR?}") ${normal?}"
 			((padding += 1))
 		fi
 		if [[ "${LAST_SEGMENT_COLOR}" -eq "${params[1]:-}" ]]; then
diff --git a/themes/powerline-plain/powerline-plain.base.bash b/themes/powerline-plain/powerline-plain.base.bash
index c077a089fc..08b81b5fc6 100644
--- a/themes/powerline-plain/powerline-plain.base.bash
+++ b/themes/powerline-plain/powerline-plain.base.bash
@@ -1,8 +1,12 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 . "$BASH_IT/themes/powerline/powerline.base.bash"
 
 function __powerline_left_segment {
 	local OLD_IFS="${IFS}"
 	IFS="|"
+	# shellcheck disable=SC2206
 	local params=($1)
 	IFS="${OLD_IFS}"
 	local pad_before_segment=" "
@@ -18,11 +22,11 @@ function __powerline_left_segment {
 		# Since the previous segment wasn't the last segment, add padding, if needed
 		#
 		if [[ "${POWERLINE_COMPACT_BEFORE_SEPARATOR}" -eq 0 ]]; then
-			LEFT_PROMPT+="$(set_color - ${LAST_SEGMENT_COLOR}) ${normal}"
+			LEFT_PROMPT+="$(set_color - "${LAST_SEGMENT_COLOR}") ${normal?}"
 		fi
 	fi
 
-	LEFT_PROMPT+="$(set_color - ${params[1]})${pad_before_segment}${params[0]}${normal}"
+	LEFT_PROMPT+="$(set_color - "${params[1]}")${pad_before_segment}${params[0]}${normal?}"
 	LAST_SEGMENT_COLOR=${params[1]}
 	((SEGMENTS_AT_LEFT += 1))
 }
@@ -39,11 +43,12 @@ function __powerline_prompt_command {
 
 	## left prompt ##
 	for segment in $POWERLINE_PROMPT; do
-		local info="$(__powerline_${segment}_prompt)"
+		local info
+		info="$(__powerline_"${segment}"_prompt)"
 		[[ -n "${info}" ]] && __powerline_left_segment "${info}"
 	done
 
-	[[ "${last_status}" -ne 0 ]] && __powerline_left_segment $(__powerline_last_status_prompt ${last_status})
+	[[ "${last_status}" -ne 0 ]] && __powerline_left_segment "$(__powerline_last_status_prompt "${last_status}")"
 
 	if [[ -n "${LEFT_PROMPT}" ]] && [[ "${POWERLINE_COMPACT_AFTER_LAST_SEGMENT}" -eq 0 ]]; then
 		__powerline_left_last_segment_padding
diff --git a/themes/powerline-plain/powerline-plain.theme.bash b/themes/powerline-plain/powerline-plain.theme.bash
index 675715287d..0cb0a0e92f 100644
--- a/themes/powerline-plain/powerline-plain.theme.bash
+++ b/themes/powerline-plain/powerline-plain.theme.bash
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 . "$BASH_IT/themes/powerline-plain/powerline-plain.base.bash"
 
diff --git a/themes/powerturk/powerturk.theme.bash b/themes/powerturk/powerturk.theme.bash
index 85f2d7ae91..01be0f19b2 100644
--- a/themes/powerturk/powerturk.theme.bash
+++ b/themes/powerturk/powerturk.theme.bash
@@ -1,4 +1,6 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # Power-Turk theme for bash-it
 # Author (C) 2015 Ahmed Seref Guneysu
 
@@ -30,11 +32,12 @@ LAST_STATUS_THEME_PROMPT_COLOR=52
 
 _collapsed_wd() {
 	# echo -e "\u2771\u276d\u276f"
-	echo $(pwd | perl -pe "
+	# shellcheck disable=SC2005
+	echo "$(pwd | perl -pe "
    BEGIN {
       binmode STDIN,  ':encoding(UTF-8)';
       binmode STDOUT, ':encoding(UTF-8)';
-   }; s|^$HOME|<HOME>|g; s|/([^/])[^/]*(?=/)|/\$1|g") \
+   }; s|^$HOME|<HOME>|g; s|/([^/])[^/]*(?=/)|/\$1|g")" \
 		| sed -re "s/\//  /g"
 }
 
@@ -45,22 +48,22 @@ _swd() {
 	current=""          # The section of the path we're currently working on.
 	end="${2:-${PWD}}/" # The unmodified rest of the path.
 
-	if [[ "$end" =~ "$HOME" ]]; then
+	if [[ "$end" == "$HOME"* ]]; then
 		INHOME=1
-		end="${end#$HOME}" #strip /home/username from start of string
-		begin="$HOME"      #start expansion from the right spot
+		end="${end#"$HOME"}" #strip /home/username from start of string
+		begin="${HOME}"      #start expansion from the right spot
 	else
 		INHOME=0
 	fi
 
-	end="${end#/}"       # Strip the first /
-	shortenedpath="$end" # The whole path, to check the length.
+	end="${end#/}"         # Strip the first /
+	shortenedpath="${end}" # The whole path, to check the length.
 	maxlength="${1:-0}"
 
 	shopt -q nullglob && NGV="-s" || NGV="-u" # Store the value for later.
 	shopt -s nullglob                         # Without this, anything that doesn't exist in the filesystem turns into */*/*/...
 
-	while [[ "$end" ]] && ((${#shortenedpath} > maxlength)); do
+	while [[ "${end}" ]] && ((${#shortenedpath} > maxlength)); do
 		current="${end%%/*}" # everything before the first /
 		end="${end#*/}"      # everything after the first /
 
@@ -69,10 +72,10 @@ _swd() {
 
 		for ((i = ${#current} - 2; i >= 0; i--)); do
 			subcurrent="${current:0:i}"
-			matching=("$begin/$subcurrent"*)  # Array of all files that start with $subcurrent.
-			((${#matching[*]} != 1)) && break # Stop shortening if more than one file matches.
-			shortcur="$subcurrent"
-			shortcurstar="$subcurrent*"
+			matching=("${begin}/${subcurrent}"*) # Array of all files that start with $subcurrent.
+			((${#matching[*]} != 1)) && break    # Stop shortening if more than one file matches.
+			shortcur="${subcurrent}"
+			shortcurstar="${subcurrent}*"
 		done
 
 		#advance
@@ -86,6 +89,7 @@ _swd() {
 
 	# Replaces slashes with  except first occurence.
 	if [ $INHOME -eq 1 ]; then
+		# shellcheck disable=SC2088
 		echo "~/$shortenedpath" | sed "s/\///2g" # make sure it starts with ~/
 	else
 		echo "/$shortenedpath" | sed "s/\///2g" # Make sure it starts with /
@@ -107,10 +111,10 @@ function set_rgb_color {
 
 function powerline_shell_prompt {
 	if [[ -n "${SSH_CLIENT}" ]]; then
-		SHELL_PROMPT="${bold_white}$(set_rgb_color - ${SHELL_SSH_THEME_PROMPT_COLOR}) ${SHELL_SSH_CHAR}\u@\h ${normal}"
+		SHELL_PROMPT="${bold_white?}$(set_rgb_color - ${SHELL_SSH_THEME_PROMPT_COLOR}) ${SHELL_SSH_CHAR}\u@\h ${normal?}"
 		LAST_THEME_COLOR=${SHELL_SSH_THEME_PROMPT_COLOR}
 	else
-		SHELL_PROMPT="${bold_white}$(set_rgb_color - ${SHELL_THEME_PROMPT_COLOR}) ${normal}"
+		SHELL_PROMPT="${bold_white?}$(set_rgb_color - ${SHELL_THEME_PROMPT_COLOR}) ${normal?}"
 		LAST_THEME_COLOR=${SHELL_THEME_PROMPT_COLOR}
 	fi
 }
@@ -125,7 +129,7 @@ function powerline_virtualenv_prompt {
 	fi
 
 	if [[ -n "$environ" ]]; then
-		VIRTUALENV_PROMPT="$(set_rgb_color ${LAST_THEME_COLOR} ${VIRTUALENV_THEME_PROMPT_COLOR})${THEME_PROMPT_SEPARATOR}${normal}$(set_rgb_color - ${VIRTUALENV_THEME_PROMPT_COLOR}) ${VIRTUALENV_CHAR}$environ ${normal}"
+		VIRTUALENV_PROMPT="$(set_rgb_color "${LAST_THEME_COLOR}" "${VIRTUALENV_THEME_PROMPT_COLOR}")${THEME_PROMPT_SEPARATOR}${normal?}$(set_rgb_color - "${VIRTUALENV_THEME_PROMPT_COLOR}") ${VIRTUALENV_CHAR}$environ ${normal?}"
 		LAST_THEME_COLOR=${VIRTUALENV_THEME_PROMPT_COLOR}
 	else
 		VIRTUALENV_PROMPT=""
@@ -137,18 +141,18 @@ function powerline_scm_prompt {
 
 	if [[ "${SCM_NONE_CHAR}" != "${SCM_CHAR}" ]]; then
 		if [[ "${SCM_DIRTY}" -eq 3 ]]; then
-			SCM_PROMPT="$(set_rgb_color ${SCM_THEME_PROMPT_STAGED_COLOR} ${SCM_THEME_PROMPT_COLOR})"
+			SCM_PROMPT="$(set_rgb_color "${SCM_THEME_PROMPT_STAGED_COLOR}" "${SCM_THEME_PROMPT_COLOR}")"
 		elif [[ "${SCM_DIRTY}" -eq 2 ]]; then
-			SCM_PROMPT="$(set_rgb_color ${SCM_THEME_PROMPT_UNSTAGED_COLOR} ${SCM_THEME_PROMPT_COLOR})"
+			SCM_PROMPT="$(set_rgb_color "${SCM_THEME_PROMPT_UNSTAGED_COLOR}" "${SCM_THEME_PROMPT_COLOR}")"
 		elif [[ "${SCM_DIRTY}" -eq 1 ]]; then
-			SCM_PROMPT="$(set_rgb_color ${SCM_THEME_PROMPT_DIRTY_COLOR} ${SCM_THEME_PROMPT_COLOR})"
+			SCM_PROMPT="$(set_rgb_color "${SCM_THEME_PROMPT_DIRTY_COLOR}" "${SCM_THEME_PROMPT_COLOR}")"
 		else
-			SCM_PROMPT="$(set_rgb_color ${SCM_THEME_PROMPT_CLEAN_COLOR} ${SCM_THEME_PROMPT_COLOR})"
+			SCM_PROMPT="$(set_rgb_color "${SCM_THEME_PROMPT_CLEAN_COLOR}" "${SCM_THEME_PROMPT_COLOR}")"
 		fi
 		if [[ "${SCM_GIT_CHAR}" == "${SCM_CHAR}" ]]; then
 			SCM_PROMPT+=" ${SCM_CHAR}${SCM_BRANCH}${SCM_STATE}"
 		fi
-		SCM_PROMPT="$(set_rgb_color ${LAST_THEME_COLOR} ${SCM_THEME_PROMPT_COLOR})${THEME_PROMPT_SEPARATOR}${normal}${SCM_PROMPT} ${normal}"
+		SCM_PROMPT="$(set_rgb_color "${LAST_THEME_COLOR}" "${SCM_THEME_PROMPT_COLOR}")${THEME_PROMPT_SEPARATOR}${normal?}${SCM_PROMPT} ${normal?}"
 		LAST_THEME_COLOR=${SCM_THEME_PROMPT_COLOR}
 	else
 		SCM_PROMPT=""
@@ -156,15 +160,16 @@ function powerline_scm_prompt {
 }
 
 function powerline_cwd_prompt {
-	CWD_PROMPT="$(set_rgb_color ${LAST_THEME_COLOR} ${CWD_THEME_PROMPT_COLOR})${THEME_PROMPT_SEPARATOR}$(set_rgb_color 0 ${CWD_THEME_PROMPT_COLOR}) $(_swd)${normal}$(set_rgb_color ${CWD_THEME_PROMPT_COLOR} -)${normal}"
+	# shellcheck disable=SC2119
+	CWD_PROMPT="$(set_rgb_color "${LAST_THEME_COLOR}" "${CWD_THEME_PROMPT_COLOR}")${THEME_PROMPT_SEPARATOR}$(set_rgb_color 0 "${CWD_THEME_PROMPT_COLOR}") $(_swd)${normal?}$(set_rgb_color "${CWD_THEME_PROMPT_COLOR}" -)${normal?}"
 	LAST_THEME_COLOR=${CWD_THEME_PROMPT_COLOR}
 }
 
 function powerline_last_status_prompt {
 	if [[ "$1" -eq 0 ]]; then
-		LAST_STATUS_PROMPT="$(set_rgb_color ${LAST_THEME_COLOR} -)${THEME_PROMPT_SEPARATOR}${normal}"
+		LAST_STATUS_PROMPT="$(set_rgb_color "${LAST_THEME_COLOR}" -)${THEME_PROMPT_SEPARATOR}${normal?}"
 	else
-		LAST_STATUS_PROMPT="$(set_rgb_color ${LAST_THEME_COLOR} ${LAST_STATUS_THEME_PROMPT_COLOR})${THEME_PROMPT_SEPARATOR}${normal}$(set_rgb_color - ${LAST_STATUS_THEME_PROMPT_COLOR}) ${LAST_STATUS} ${normal}$(set_rgb_color ${LAST_STATUS_THEME_PROMPT_COLOR} -)${THEME_PROMPT_SEPARATOR}${normal}"
+		LAST_STATUS_PROMPT="$(set_rgb_color "${LAST_THEME_COLOR}" "${LAST_STATUS_THEME_PROMPT_COLOR}")${THEME_PROMPT_SEPARATOR}${normal?}$(set_rgb_color - "${LAST_STATUS_THEME_PROMPT_COLOR}") ${LAST_STATUS} ${normal?}$(set_rgb_color "${LAST_STATUS_THEME_PROMPT_COLOR}" -)${THEME_PROMPT_SEPARATOR}${normal?}"
 	fi
 }
 
diff --git a/themes/primer/primer.theme.bash b/themes/primer/primer.theme.bash
index f6169cd039..13b28a5a32 100644
--- a/themes/primer/primer.theme.bash
+++ b/themes/primer/primer.theme.bash
@@ -1,11 +1,12 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 # based of the candy theme, but minimized by odbol
 function prompt_command() {
-	PS1="$(clock_prompt) ${reset_color}${white}\w${reset_color}$(scm_prompt_info)${blue} →${bold_blue} ${reset_color} "
+	PS1="$(clock_prompt) ${reset_color?}${white?}\w${reset_color?}$(scm_prompt_info)${blue?} →${bold_blue?} ${reset_color?} "
 }
 
-THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"$blue"}
+THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"${blue?}"}
 THEME_CLOCK_FORMAT=${THEME_CLOCK_FORMAT:-"%I:%M:%S"}
 
 safe_append_prompt_command prompt_command
diff --git a/themes/pro/pro.theme.bash b/themes/pro/pro.theme.bash
index 449915bb34..8dd128233a 100644
--- a/themes/pro/pro.theme.bash
+++ b/themes/pro/pro.theme.bash
@@ -1,14 +1,15 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
-SCM_THEME_PROMPT_DIRTY=" ${red}✗"
-SCM_THEME_PROMPT_CLEAN=" ${green}✓"
-SCM_THEME_PROMPT_PREFIX=" ${blue}scm:( "
-SCM_THEME_PROMPT_SUFFIX="${blue} )"
+SCM_THEME_PROMPT_DIRTY=" ${red?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${green?}✓"
+SCM_THEME_PROMPT_PREFIX=" ${blue?}scm:( "
+SCM_THEME_PROMPT_SUFFIX="${blue?} )"
 
-GIT_THEME_PROMPT_DIRTY=" ${red}✗"
-GIT_THEME_PROMPT_CLEAN=" ${green}✓"
-GIT_THEME_PROMPT_PREFIX="${green}git:( "
-GIT_THEME_PROMPT_SUFFIX="${green} )"
+GIT_THEME_PROMPT_DIRTY=" ${red?}✗"
+GIT_THEME_PROMPT_CLEAN=" ${green?}✓"
+GIT_THEME_PROMPT_PREFIX="${green?}git:( "
+GIT_THEME_PROMPT_SUFFIX="${green?} )"
 
 function git_prompt_info {
 	git_prompt_vars
@@ -16,7 +17,7 @@ function git_prompt_info {
 }
 
 function prompt() {
-	PS1="\h: \W $(scm_prompt_info)${reset_color} $ "
+	PS1="\h: \W $(scm_prompt_info)${reset_color?} $ "
 }
 
 safe_append_prompt_command prompt
diff --git a/themes/purity/purity.theme.bash b/themes/purity/purity.theme.bash
index 0fc6c4cfa8..c2b78a5944 100644
--- a/themes/purity/purity.theme.bash
+++ b/themes/purity/purity.theme.bash
@@ -13,7 +13,7 @@ GIT_THEME_PROMPT_SUFFIX=" ${reset_color?})"
 
 STATUS_THEME_PROMPT_BAD="${bold_red?}❯${reset_color?}${normal?} "
 STATUS_THEME_PROMPT_OK="${bold_green?}❯${reset_color?}${normal?} "
-: "${PURITY_THEME_PROMPT_COLOR:=$blue}"
+: "${PURITY_THEME_PROMPT_COLOR:=${blue?}}"
 
 function venv_prompt() {
 	python_venv=""
diff --git a/themes/radek/radek.theme.bash b/themes/radek/radek.theme.bash
index 7983121174..6b5f1222ac 100644
--- a/themes/radek/radek.theme.bash
+++ b/themes/radek/radek.theme.bash
@@ -1,19 +1,20 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
-GIT_THEME_PROMPT_DIRTY="${red}✗"
-GIT_THEME_PROMPT_CLEAN="${bold_green}✓"
-GIT_THEME_PROMPT_PREFIX="${bold_cyan}["
-GIT_THEME_PROMPT_SUFFIX="${bold_cyan}]"
+GIT_THEME_PROMPT_DIRTY="${red?}✗"
+GIT_THEME_PROMPT_CLEAN="${bold_green?}✓"
+GIT_THEME_PROMPT_PREFIX="${bold_cyan?}["
+GIT_THEME_PROMPT_SUFFIX="${bold_cyan?}]"
 
-VIRTUALENV_THEME_PROMPT_PREFIX="${bold_green}["
-VIRTUALENV_THEME_PROMPT_SUFFIX="${bold_green}]"
-CONDAENV_THEME_PROMPT_PREFIX="${bold_green}["
-CONDAENV_THEME_PROMPT_SUFFIX="${bold_green}]"
-PYTHON_THEME_PROMPT_PREFIX="${bold_green}["
-PYTHON_THEME_PROMPT_SUFFIX="${bold_green}]"
+VIRTUALENV_THEME_PROMPT_PREFIX="${bold_green?}["
+VIRTUALENV_THEME_PROMPT_SUFFIX="${bold_green?}]"
+CONDAENV_THEME_PROMPT_PREFIX="${bold_green?}["
+CONDAENV_THEME_PROMPT_SUFFIX="${bold_green?}]"
+PYTHON_THEME_PROMPT_PREFIX="${bold_green?}["
+PYTHON_THEME_PROMPT_SUFFIX="${bold_green?}]"
 
 function prompt_command() {
-	PS1="\n${bold_white}[\u@\h]${bold_yellow}[\w] ${bold_cyan}$(scm_prompt_char_info)$(python_version_prompt)${green}\n→${reset_color} "
+	PS1="\n${bold_white?}[\u@\h]${bold_yellow?}[\w] ${bold_cyan?}$(scm_prompt_char_info)$(python_version_prompt)${green?}\n→${reset_color?} "
 }
 
 safe_append_prompt_command prompt_command
diff --git a/themes/rainbowbrite/rainbowbrite.theme.bash b/themes/rainbowbrite/rainbowbrite.theme.bash
index 37cab72412..45f29f8223 100644
--- a/themes/rainbowbrite/rainbowbrite.theme.bash
+++ b/themes/rainbowbrite/rainbowbrite.theme.bash
@@ -1,4 +1,5 @@
 # shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 # based off of n0qorg
 # looks like, if you're in a git repo:
@@ -9,9 +10,9 @@ prompt_setter() {
 	# Save history
 	_save-and-reload-history 1
 	# displays user@server in purple
-	# PS1="$red$(scm_char) $purple\u@\h$reset_color:$blue\w$yellow$(scm_prompt_info)$(ruby_version_prompt) $black\$$reset_color "
+	# PS1="${red?}$(scm_char) ${purple?}\u@\h${reset_color?}:${blue?}\w${yellow?}$(scm_prompt_info)$(ruby_version_prompt) ${black?}\$${reset_color?} "
 	# no user@server
-	PS1="$red$(scm_char) $blue\w$yellow$(scm_prompt_info)$(ruby_version_prompt) $black\$$reset_color "
+	PS1="${red?}$(scm_char) ${blue?}\w${yellow?}$(scm_prompt_info)$(ruby_version_prompt) ${black?}\$${reset_color?} "
 	PS2='> '
 	PS4='+ '
 }
@@ -19,9 +20,9 @@ prompt_setter() {
 safe_append_prompt_command prompt_setter
 
 SCM_NONE_CHAR='·'
-SCM_THEME_PROMPT_DIRTY=" ${red}✗"
-SCM_THEME_PROMPT_CLEAN=" ${green}✓"
+SCM_THEME_PROMPT_DIRTY=" ${red?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${green?}✓"
 SCM_THEME_PROMPT_PREFIX=" ("
-SCM_THEME_PROMPT_SUFFIX="${yellow})"
+SCM_THEME_PROMPT_SUFFIX="${yellow?})"
 RVM_THEME_PROMPT_PREFIX=" ("
 RVM_THEME_PROMPT_SUFFIX=")"
diff --git a/themes/ramses/ramses.theme.bash b/themes/ramses/ramses.theme.bash
index ee4fdbdab1..c025c84d91 100644
--- a/themes/ramses/ramses.theme.bash
+++ b/themes/ramses/ramses.theme.bash
@@ -1,11 +1,14 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
-SCM_GIT_CHAR="${bold_green}±${normal}"
-SCM_SVN_CHAR="${bold_cyan}⑆${normal}"
-SCM_HG_CHAR="${bold_red}☿${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
+SCM_GIT_CHAR="${bold_green?}±${normal?}"
+SCM_SVN_CHAR="${bold_cyan?}⑆${normal?}"
+SCM_HG_CHAR="${bold_red?}☿${normal?}"
 
 #Mysql Prompt
 export MYSQL_PS1="(\u@\h) [\d]> "
@@ -22,23 +25,24 @@ esac
 PS3=">> "
 
 __my_rvm_ruby_version() {
-	local gemset=$(echo $GEM_HOME | awk -F'@' '{print $2}')
-	[ "$gemset" != "" ] && gemset="@$gemset"
-	local version=$(echo $MY_RUBY_HOME | awk -F'-' '{print $2}')
+	local version gemset
+	gemset=$(echo "$GEM_HOME" | awk -F'@' '{print $2}')
+	[[ -n "$gemset" ]] && gemset="@$gemset"
+	version=$(echo "$MY_RUBY_HOME" | awk -F'-' '{print $2}')
 	local full="$version$gemset"
-	[ "$full" != "" ] && echo "[$full]"
+	[[ -n "$full" ]] && echo "[$full]"
 }
 
 is_vim_shell() {
-	if [ ! -z "$VIMRUNTIME" ]; then
-		echo "[${cyan}vim shell${normal}]"
+	if [[ -n "$VIMRUNTIME" ]]; then
+		echo "[${cyan?}vim shell${normal?}]"
 	fi
 }
 
 # show chroot if exist
 chroot() {
-	if [ -n "$debian_chroot" ]; then
-		my_ps_chroot="${bold_cyan}$debian_chroot${normal}"
+	if [[ -n "$debian_chroot" ]]; then
+		my_ps_chroot="${bold_cyan?}$debian_chroot${normal?}"
 		echo "($my_ps_chroot)"
 	fi
 }
@@ -46,11 +50,11 @@ chroot() {
 # show virtualenvwrapper
 my_ve() {
 
-	if [ -n "$CONDA_DEFAULT_ENV" ]; then
-		my_ps_ve="${bold_purple}${CONDA_DEFAULT_ENV}${normal}"
+	if [[ -n "$CONDA_DEFAULT_ENV" ]]; then
+		my_ps_ve="${bold_purple?}${CONDA_DEFAULT_ENV}${normal?}"
 		echo "($my_ps_ve)"
 	elif [ -n "$VIRTUAL_ENV" ]; then
-		my_ps_ve="${bold_purple}$ve${normal}"
+		my_ps_ve="${bold_purple?}$ve${normal?}"
 		echo "($my_ps_ve)"
 	fi
 	echo ""
@@ -58,12 +62,12 @@ my_ve() {
 
 prompt() {
 	SCM_PROMPT_FORMAT='[%s][%s]'
-	my_ps_host="${green}\h${normal}"
+	my_ps_host="${green?}\h${normal?}"
 	# yes, these are the the same for now ...
-	my_ps_host_root="${green}\h${normal}"
+	my_ps_host_root="${green?}\h${normal?}"
 
-	my_ps_user="${bold_green}\u${normal}"
-	my_ps_root="${bold_red}\u${normal}"
+	my_ps_user="${bold_green?}\u${normal?}"
+	my_ps_root="${bold_red?}\u${normal?}"
 
 	if [ -n "$VIRTUAL_ENV" ]; then
 		ve=$(basename "$VIRTUAL_ENV")
@@ -72,12 +76,12 @@ prompt() {
 	# nice prompt
 	case "$(id -u)" in
 		0)
-			PS1="${TITLEBAR}┌─$(my_ve)$(chroot)[$my_ps_root][$my_ps_host_root]$(scm_prompt)$(__my_rvm_ruby_version)[${cyan}\w${normal}]
+			PS1="${TITLEBAR}┌─$(my_ve)$(chroot)[$my_ps_root][$my_ps_host_root]$(scm_prompt)$(__my_rvm_ruby_version)[${cyan?}\w${normal?}]
 ▪ "
 			;;
 		*)
 			PS1="${TITLEBAR}┌─$(my_ve)$(chroot)[$my_ps_user][$my_ps_host]$(scm_prompt)$(__my_rvm_ruby_version)
-|─[${bold_purple}\w${normal}]
+|─[${bold_purple?}\w${normal?}]
 ▪ "
 			;;
 	esac
diff --git a/themes/rana/rana.theme.bash b/themes/rana/rana.theme.bash
index 41b7bba446..aa35bcc0c2 100644
--- a/themes/rana/rana.theme.bash
+++ b/themes/rana/rana.theme.bash
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034,SC2312 # Expected behavior for themes.
 
 # Theme inspired on:
 #  - Ronacher's dotfiles (mitsuhikos) - http://github.com/mitsuhiko/dotfiles/tree/master/bash/
@@ -11,24 +12,24 @@
 
 # For the real Monokai colors you should add these to your .XDefaults or
 # terminal configuration:
-#! ----------------------------------------------------------- TERMINAL COLORS
-#! monokai - http://www.monokai.nl/blog/2006/07/15/textmate-color-theme/
+# ----------------------------------------------------------- TERMINAL COLORS
+# monokai - http://www.monokai.nl/blog/2006/07/15/textmate-color-theme/
 #*background: #272822
 #*foreground: #E2DA6E
 #*color0: black
-#! mild red
+# mild red
 #*color1: #CD0000
-#! light green
+# light green
 #*color2: #A5E02D
-#! orange (yellow)
+# orange (yellow)
 #*color3: #FB951F
-#! "dark" blue
+# "dark" blue
 #*color4: #076BCC
-#! hot pink
+# hot pink
 #*color5: #F6266C
-#! cyan
+# cyan
 #*color6: #64D9ED
-#! gray
+# gray
 #*color7: #E5E5E5
 
 # ----------------------------------------------------------------- DEF COLOR
@@ -89,14 +90,14 @@ case $TERM in
 esac
 
 is_vim_shell() {
-	if [ ! -z "$VIMRUNTIME" ]; then
+	if [[ -n "$VIMRUNTIME" ]]; then
 		echo "${D_INTERMEDIATE_COLOR}on ${D_VIMSHELL_COLOR}\
 vim shell${D_DEFAULT_COLOR} "
 	fi
 }
 
 mitsuhikos_lastcommandfailed() {
-	code=$?
+	local code=$?
 	if [ $code != 0 ]; then
 		echo "${D_INTERMEDIATE_COLOR}exited ${D_CMDFAIL_COLOR}\
 $code ${D_DEFAULT_COLOR}"
@@ -105,7 +106,7 @@ $code ${D_DEFAULT_COLOR}"
 
 # vcprompt for scm instead of bash_it default
 demula_vcprompt() {
-	if [ ! -z "$VCPROMPT_EXECUTABLE" ]; then
+	if [[ -n "$VCPROMPT_EXECUTABLE" ]]; then
 		local D_VCPROMPT_FORMAT="on ${D_SCM_COLOR}%s${D_INTERMEDIATE_COLOR}:\
 ${D_BRANCH_COLOR}%b %r ${D_CHANGES_COLOR}%m%u ${D_DEFAULT_COLOR}"
 		$VCPROMPT_EXECUTABLE -f "$D_VCPROMPT_FORMAT"
@@ -117,10 +118,7 @@ prompt_git() {
 	local branchName=''
 
 	# Check if the current directory is in a Git repository.
-	if [ $(
-		git rev-parse --is-inside-work-tree &> /dev/null
-		echo "${?}"
-	) == '0' ]; then
+	if git rev-parse --is-inside-work-tree &> /dev/null; then
 
 		# check if the current directory is in .git before running git checks
 		if [ "$(git rev-parse --is-inside-git-dir 2> /dev/null)" == 'false' ]; then
@@ -129,22 +127,22 @@ prompt_git() {
 			git update-index --really-refresh -q &> /dev/null
 
 			# Check for uncommitted changes in the index.
-			if ! $(git diff --quiet --ignore-submodules --cached); then
+			if ! git diff --quiet --ignore-submodules --cached; then
 				s+='+'
 			fi
 
 			# Check for unstaged changes.
-			if ! $(git diff-files --quiet --ignore-submodules --); then
+			if ! git diff-files --quiet --ignore-submodules --; then
 				s+='!'
 			fi
 
 			# Check for untracked files.
-			if [ -n "$(git ls-files --others --exclude-standard)" ]; then
+			if [[ -n "$(git ls-files --others --exclude-standard)" ]]; then
 				s+='?'
 			fi
 
 			# Check for stashed files.
-			if $(git rev-parse --verify refs/stash &> /dev/null); then
+			if git rev-parse --verify refs/stash &> /dev/null; then
 				s+='$'
 			fi
 
@@ -157,7 +155,7 @@ prompt_git() {
 			|| git rev-parse --short HEAD 2> /dev/null \
 			|| echo '(unknown)')"
 
-		[ -n "${s}" ] && s=" [${s}]"
+		[[ -n "${s}" ]] && s=" [${s}]"
 
 		echo -e "${1}${branchName}${Cya}${s}"
 	else
@@ -167,13 +165,14 @@ prompt_git() {
 
 # -------------------------------------------------------------- PROMPT OUTPUT
 prompt() {
-	local LAST_COMMAND_FAILED=$(mitsuhikos_lastcommandfailed)
+	local LAST_COMMAND_FAILED
+	LAST_COMMAND_FAILED=$(mitsuhikos_lastcommandfailed)
 	local SAVE_CURSOR='\033[s'
 	local RESTORE_CURSOR='\033[u'
 	local MOVE_CURSOR_RIGHTMOST='\033[500C'
 	local MOVE_CURSOR_5_LEFT='\033[5D'
 
-	if [[ "$OSTYPE" == 'linux'* ]]; then
+	if [[ "${OSTYPE}" == 'linux'* ]]; then
 		PS1="${TITLEBAR}
 ${SAVE_CURSOR}${MOVE_CURSOR_RIGHTMOST}${MOVE_CURSOR_5_LEFT}\
 $(battery_charge)${RESTORE_CURSOR}\
diff --git a/themes/redline/redline.theme.bash b/themes/redline/redline.theme.bash
index 65bf6f0a55..0a68f5f58e 100644
--- a/themes/redline/redline.theme.bash
+++ b/themes/redline/redline.theme.bash
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 . "$BASH_IT/themes/powerline/powerline.base.bash"
 
diff --git a/themes/rjorgenson/rjorgenson.theme.bash b/themes/rjorgenson/rjorgenson.theme.bash
index c41ebff025..7f5ce5cebb 100644
--- a/themes/rjorgenson/rjorgenson.theme.bash
+++ b/themes/rjorgenson/rjorgenson.theme.bash
@@ -5,17 +5,17 @@
 
 # set colors for use throughout the prompt
 # i like things consistent
-BRACKET_COLOR=${blue}
-STRING_COLOR=${green}
+BRACKET_COLOR=${blue?}
+STRING_COLOR=${green?}
 
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
-SCM_GIT_CHAR="${STRING_COLOR}±${normal}"
-SCM_SVN_CHAR="${bold_cyan}⑆${normal}"
-SCM_HG_CHAR="${bold_red}☿${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
+SCM_GIT_CHAR="${STRING_COLOR}±${normal?}"
+SCM_SVN_CHAR="${bold_cyan?}⑆${normal?}"
+SCM_HG_CHAR="${bold_red?}☿${normal?}"
 
 #Mysql Prompt
 export MYSQL_PS1="(\u@\h) [\d]> "
@@ -37,12 +37,12 @@ __my_rvm_ruby_version() {
 	[[ "$gemset" != "" ]] && gemset="@$gemset"
 	version=$(echo "$MY_RUBY_HOME" | awk -F'-' '{print $2}')
 	full="$version$gemset"
-	[[ "$full" != "" ]] && echo "${BRACKET_COLOR}[${STRING_COLOR}$full${BRACKET_COLOR}]${normal}"
+	[[ "$full" != "" ]] && echo "${BRACKET_COLOR}[${STRING_COLOR}$full${BRACKET_COLOR}]${normal?}"
 }
 
 is_vim_shell() {
 	if [[ -n "$VIMRUNTIME" ]]; then
-		echo "${BRACKET_COLOR}[${STRING_COLOR}vim shell${BRACKET_COLOR}]${normal}"
+		echo "${BRACKET_COLOR}[${STRING_COLOR}vim shell${BRACKET_COLOR}]${normal?}"
 	fi
 }
 
@@ -55,32 +55,32 @@ todo_txt_count() {
 	if hash todo.sh 2>&-; then # is todo.sh installed
 		count=$(todo.sh ls | grep -E "TODO: [0-9]+ of ([0-9]+) tasks shown" | awk '{ print $4 }')
 		if is_integer "$count"; then # did we get a sane answer back
-			echo "${BRACKET_COLOR}[${STRING_COLOR}T:$count${BRACKET_COLOR}]$normal"
+			echo "${BRACKET_COLOR}[${STRING_COLOR}T:$count${BRACKET_COLOR}]${normal?}"
 		fi
 	fi
 }
 
 my_prompt_char() {
 	if [[ $OSTYPE =~ "darwin" ]]; then
-		echo "${BRACKET_COLOR}➞  ${normal}"
+		echo "${BRACKET_COLOR}➞  ${normal?}"
 	else
-		echo "${BRACKET_COLOR}➞ ${normal}"
+		echo "${BRACKET_COLOR}➞ ${normal?}"
 	fi
 }
 
 prompt() {
 	SCM_PROMPT_FORMAT="${BRACKET_COLOR}[%s${BRACKET_COLOR}][${STRING_COLOR}%s${BRACKET_COLOR}]"
 
-	my_ps_host="${STRING_COLOR}\h${normal}"
-	my_ps_user="${STRING_COLOR}\u${normal}"
-	my_ps_root="${bold_red}\u${normal}"
-	my_ps_path="${STRING_COLOR}\w${normal}"
+	my_ps_host="${STRING_COLOR}\h${normal?}"
+	my_ps_user="${STRING_COLOR}\u${normal?}"
+	my_ps_root="${bold_red?}\u${normal?}"
+	my_ps_path="${STRING_COLOR}\w${normal?}"
 
 	# nice prompt
 	case "$(id -u)" in
 		0)
 			PS1="${TITLEBAR}${BRACKET_COLOR}┌─[$my_ps_root${BRACKET_COLOR}][$my_ps_host${BRACKET_COLOR}]$(scm_prompt)$(__my_rvm_ruby_version)${BRACKET_COLOR}[${STRING_COLOR}\w${BRACKET_COLOR}]$(is_vim_shell)
-${BRACKET_COLOR}└─$(my_prompt_char)${normal}"
+${BRACKET_COLOR}└─$(my_prompt_char)${normal?}"
 			;;
 		*)
 			PS1="${TITLEBAR}${BRACKET_COLOR}┌─[$my_ps_user${BRACKET_COLOR}][$my_ps_host${BRACKET_COLOR}]$(scm_prompt)$(__my_rvm_ruby_version)${BRACKET_COLOR}[${STRING_COLOR}\w${BRACKET_COLOR}]$(is_vim_shell)
diff --git a/themes/robbyrussell/robbyrussell.theme.bash b/themes/robbyrussell/robbyrussell.theme.bash
index 11aa5ef673..542361783d 100644
--- a/themes/robbyrussell/robbyrussell.theme.bash
+++ b/themes/robbyrussell/robbyrussell.theme.bash
@@ -1,14 +1,15 @@
 # shellcheck shell=bash
 # shellcheck disable=SC2034,SC2154
-SCM_THEME_PROMPT_DIRTY=" ${bold_yellow}✗"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓"
-SCM_THEME_PROMPT_PREFIX=" ${bold_blue}scm:("
-SCM_THEME_PROMPT_SUFFIX="${bold_blue})"
 
-GIT_THEME_PROMPT_DIRTY=" ${bold_yellow}✗"
-GIT_THEME_PROMPT_CLEAN=" ${bold_green}✓"
-GIT_THEME_PROMPT_PREFIX=" ${bold_blue}git:("
-GIT_THEME_PROMPT_SUFFIX="${bold_blue})"
+SCM_THEME_PROMPT_DIRTY=" ${bold_yellow?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓"
+SCM_THEME_PROMPT_PREFIX=" ${bold_blue?}scm:("
+SCM_THEME_PROMPT_SUFFIX="${bold_blue?})"
+
+GIT_THEME_PROMPT_DIRTY=" ${bold_yellow?}✗"
+GIT_THEME_PROMPT_CLEAN=" ${bold_green?}✓"
+GIT_THEME_PROMPT_PREFIX=" ${bold_blue?}git:("
+GIT_THEME_PROMPT_SUFFIX="${bold_blue?})"
 
 RVM_THEME_PROMPT_PREFIX="|"
 RVM_THEME_PROMPT_SUFFIX="|"
@@ -18,11 +19,11 @@ VIRTUALENV_THEME_PROMPT_SUFFIX=') '
 
 function git_prompt_info() {
 	git_prompt_vars
-	echo -e "$SCM_PREFIX${bold_red}$SCM_BRANCH$SCM_STATE$SCM_SUFFIX"
+	echo -e "$SCM_PREFIX${bold_red?}$SCM_BRANCH$SCM_STATE$SCM_SUFFIX"
 }
 
 function prompt_command() {
-	PS1="$(conda_or_venv_prompt)${bold_green}➜  ${bold_cyan}\W${reset_color}$(scm_prompt_info)${normal} "
+	PS1="$(conda_or_venv_prompt)${bold_green?}➜  ${bold_cyan?}\W${reset_color?}$(scm_prompt_info)${normal?} "
 }
 
 PROMPT_COMMAND=prompt_command
diff --git a/themes/roderik/roderik.theme.bash b/themes/roderik/roderik.theme.bash
index cb7252784e..8a6fd2a85a 100644
--- a/themes/roderik/roderik.theme.bash
+++ b/themes/roderik/roderik.theme.bash
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 export GIT_PS1_SHOWDIRTYSTATE=true
 export GIT_PS1_SHOWUNTRACKEDFILES=true
@@ -8,9 +9,9 @@ export PROMPT_DIRTRIM=3
 
 function prompt_command() {
 	if [[ ${EUID} == 0 ]]; then
-		PS1="[$(clock_prompt)]${yellow}[${red}\u@\h ${green}\w${yellow}]${red}$(__git_ps1 "(%s)")${normal}\\$ "
+		PS1="[$(clock_prompt)]${yellow?}[${red?}\u@\h ${green?}\w${yellow?}]${red?}$(__git_ps1 "(%s)")${normal?}\\$ "
 	else
-		PS1="[$(clock_prompt)]${yellow}[${cyan}\u@\h ${green}\w${yellow}]${red}$(__git_ps1 "(%s)")${normal}\\$ "
+		PS1="[$(clock_prompt)]${yellow?}[${cyan?}\u@\h ${green?}\w${yellow?}]${red?}$(__git_ps1 "(%s)")${normal?}\\$ "
 	fi
 }
 
diff --git a/themes/sexy/sexy.theme.bash b/themes/sexy/sexy.theme.bash
index 6a59c66528..6dc4664b59 100644
--- a/themes/sexy/sexy.theme.bash
+++ b/themes/sexy/sexy.theme.bash
@@ -1,3 +1,6 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # Sexy Bash Prompt, inspired by "Extravagant Zsh Prompt"
 # Screenshot: http://cloud.gf3.ca/M5rG
 # A big thanks to \amethyst on Freenode
diff --git a/themes/simple/simple.theme.bash b/themes/simple/simple.theme.bash
index 5f34636c58..8d38c0fa3e 100644
--- a/themes/simple/simple.theme.bash
+++ b/themes/simple/simple.theme.bash
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 # prompt themeing
 
@@ -13,7 +14,7 @@ case $TERM in
 esac
 
 function prompt_command() {
-	PS1="${TITLEBAR}${orange}${reset_color}${green}\w${bold_blue}\[$(scm_prompt_info)\]${normal} "
+	PS1="${TITLEBAR}${orange?}${reset_color?}${green?}\w${bold_blue?}\[$(scm_prompt_info)\]${normal?} "
 }
 
 # scm themeing
diff --git a/themes/sirup/sirup.theme.bash b/themes/sirup/sirup.theme.bash
index 73e957837f..47f620260e 100644
--- a/themes/sirup/sirup.theme.bash
+++ b/themes/sirup/sirup.theme.bash
@@ -1,22 +1,22 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # For unstaged(*) and staged(+) values next to branch name in __git_ps1
 GIT_PS1_SHOWDIRTYSTATE="enabled"
 
 function rvm_version_prompt {
-	local gemset=$(echo $GEM_HOME | awk -F'@' '{print $2}')
-
-	[ "$gemset" != "" ] && gemset="@$gemset"
-	local version=$(echo $MY_RUBY_HOME | awk -F'-' '{print $2}')
-
-	[ "$version" == "1.9.2" ] && version=""
-
+	local gemset version
+	gemset=$(echo "$GEM_HOME" | awk -F'@' '{print $2}')
+	[[ -n "$gemset" ]] && gemset="@$gemset"
+	version=$(echo "$MY_RUBY_HOME" | awk -F'-' '{print $2}')
+	[[ "$version" == "1.9.2" ]] && version=""
 	local full="$version$gemset"
-
-	[ "$full" != "" ] && echo "$full"
+	[[ -n "$full" ]] && echo "$full"
 }
 
 function prompt_command() {
 	# Check http://github.com/Sirupsen/dotfiles for screenshot
-	PS1="$blue\W/$bold_blue$(rvm_version_prompt)$bold_green$(__git_ps1 " (%s)") ${normal}$ "
+	PS1="${blue?}\W/${bold_blue?}$(rvm_version_prompt)${bold_green?}$(__git_ps1 " (%s)") ${normal?}$ "
 }
 
 safe_append_prompt_command prompt_command
diff --git a/themes/slick/slick.theme.bash b/themes/slick/slick.theme.bash
index f4b59aa14a..bb75f09dee 100644
--- a/themes/slick/slick.theme.bash
+++ b/themes/slick/slick.theme.bash
@@ -1,11 +1,14 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
-SCM_GIT_CHAR="${bold_cyan}±${normal}"
-SCM_SVN_CHAR="${bold_green}⑆${normal}"
-SCM_HG_CHAR="${bold_red}☿${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
+SCM_GIT_CHAR="${bold_cyan?}±${normal?}"
+SCM_SVN_CHAR="${bold_green?}⑆${normal?}"
+SCM_HG_CHAR="${bold_red?}☿${normal?}"
 
 #Mysql Prompt
 export MYSQL_PS1="(\u@\h) [\d]> "
@@ -22,22 +25,23 @@ esac
 PS3=">> "
 
 __my_rvm_ruby_version() {
-	local gemset=$(echo $GEM_HOME | awk -F'@' '{print $2}')
-	[ "$gemset" != "" ] && gemset="@$gemset"
-	local version=$(echo $MY_RUBY_HOME | awk -F'-' '{print $2}')
+	local gemset version
+	gemset=$(echo "$GEM_HOME" | awk -F'@' '{print $2}')
+	[[ "$gemset" ]] && gemset="@$gemset"
+	version=$(echo "$MY_RUBY_HOME" | awk -F'-' '{print $2}')
 	local full="$version$gemset"
-	[ "$full" != "" ] && echo "[$full]"
+	[[ "$full" ]] && echo "[$full]"
 }
 
 __my_venv_prompt() {
-	if [ ! -z "$VIRTUAL_ENV" ]; then
-		echo "[${blue}@${normal}${VIRTUAL_ENV##*/}]"
+	if [[ -n "$VIRTUAL_ENV" ]]; then
+		echo "[${blue?}@${normal?}${VIRTUAL_ENV##*/}]"
 	fi
 }
 
 is_vim_shell() {
-	if [ ! -z "$VIMRUNTIME" ]; then
-		echo "[${cyan}vim shell${normal}]"
+	if [[ -n "$VIMRUNTIME" ]]; then
+		echo "[${cyan?}vim shell${normal?}]"
 	fi
 }
 
@@ -45,13 +49,13 @@ prompt() {
 	SCM_PROMPT_FORMAT='[%s][%s]'
 	case $HOSTNAME in
 		"clappy"*)
-			my_ps_host="${green}\h${normal}"
+			my_ps_host="${green?}\h${normal?}"
 			;;
 		"icekernel")
-			my_ps_host="${red}\h${normal}"
+			my_ps_host="${red?}\h${normal?}"
 			;;
 		*)
-			my_ps_host="${green}\h${normal}"
+			my_ps_host="${green?}\h${normal?}"
 			;;
 	esac
 
@@ -62,11 +66,11 @@ prompt() {
 	# nice prompt
 	case "$(id -u)" in
 		0)
-			PS1="${TITLEBAR}[$my_ps_root][$my_ps_host]$(scm_prompt)$(__my_rvm_ruby_version)[${cyan}\w${normal}]$(is_vim_shell)
+			PS1="${TITLEBAR}[$my_ps_root][$my_ps_host]$(scm_prompt)$(__my_rvm_ruby_version)[${cyan?}\w${normal?}]$(is_vim_shell)
 $ "
 			;;
 		*)
-			PS1="${TITLEBAR}[$my_ps_user][$my_ps_host]$(scm_prompt)$(__my_rvm_ruby_version)$(__my_venv_prompt)[${cyan}\w${normal}]$(is_vim_shell)
+			PS1="${TITLEBAR}[$my_ps_user][$my_ps_host]$(scm_prompt)$(__my_rvm_ruby_version)$(__my_venv_prompt)[${cyan?}\w${normal?}]$(is_vim_shell)
 $ "
 			;;
 	esac
diff --git a/themes/standard/standard.theme.bash b/themes/standard/standard.theme.bash
index 1f9f8795d7..b550d5ebd3 100644
--- a/themes/standard/standard.theme.bash
+++ b/themes/standard/standard.theme.bash
@@ -1,3 +1,6 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # scm themeing
 SCM_THEME_PROMPT_DIRTY="×"
 SCM_THEME_PROMPT_CLEAN="✓"
@@ -18,7 +21,8 @@ case $TERM in
 esac
 
 function prompt_command() {
-	PROMPT='${green}\u${normal}@${green}\h${normal}:${blue}\w${normal}${red}$(prompt_char)$(git_prompt_info)${normal}\$ '
+	# shellcheck disable=SC2016
+	PROMPT='${green?}\u${normal?}@${green?}\h${normal?}:${blue?}\w${normal?}${red?}$(prompt_char)$(git_prompt_info)${normal?}\$ '
 }
 
 safe_append_prompt_command prompt_command
diff --git a/themes/tonka/tonka.theme.bash b/themes/tonka/tonka.theme.bash
index 06f091f300..63632329b9 100644
--- a/themes/tonka/tonka.theme.bash
+++ b/themes/tonka/tonka.theme.bash
@@ -1,4 +1,5 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
 __tonka_time() {
 	THEME_CLOCK_FORMAT="%H%M"
diff --git a/themes/tonotdo/tonotdo.theme.bash b/themes/tonotdo/tonotdo.theme.bash
index 63296eaad7..0334e88ed0 100644
--- a/themes/tonotdo/tonotdo.theme.bash
+++ b/themes/tonotdo/tonotdo.theme.bash
@@ -1,13 +1,14 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
 
-SCM_THEME_PROMPT_PREFIX=" ${purple}"
-SCM_THEME_PROMPT_SUFFIX=" ${normal}"
-SCM_THEME_PROMPT_DIRTY=" ${red}✗"
-SCM_THEME_PROMPT_CLEAN=" ${green}✓"
+SCM_THEME_PROMPT_PREFIX=" ${purple?}"
+SCM_THEME_PROMPT_SUFFIX=" ${normal?}"
+SCM_THEME_PROMPT_DIRTY=" ${red?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${green?}✓"
 SCM_GIT_SHOW_DETAILS="false"
 
 function prompt_command() {
-	PS1="${yellow}\u${normal}${cyan}@\h${normal}${purple} ${normal}${green}\w${normal}$(scm_prompt_info)> "
+	PS1="${yellow?}\u${normal?}${cyan?}@\h${normal?}${purple?} ${normal?}${green?}\w${normal?}$(scm_prompt_info)> "
 }
 
 safe_append_prompt_command prompt_command
diff --git a/themes/tylenol/tylenol.theme.bash b/themes/tylenol/tylenol.theme.bash
index 560be51912..9a264db3fe 100644
--- a/themes/tylenol/tylenol.theme.bash
+++ b/themes/tylenol/tylenol.theme.bash
@@ -1,12 +1,13 @@
-#!/usr/bin/env bash
-#
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # Based on 'bobby' theme with the addition of virtualenv_prompt
 #
 
-SCM_THEME_PROMPT_DIRTY=" ${red}✗"
-SCM_THEME_PROMPT_CLEAN=" ${green}✓"
-SCM_THEME_PROMPT_PREFIX=" ${yellow}|${reset_color}"
-SCM_THEME_PROMPT_SUFFIX="${yellow}|"
+SCM_THEME_PROMPT_DIRTY=" ${red?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${green?}✓"
+SCM_THEME_PROMPT_PREFIX=" ${yellow?}|${reset_color?}"
+SCM_THEME_PROMPT_SUFFIX="${yellow?}|"
 
 RVM_THEME_PROMPT_PREFIX="|"
 RVM_THEME_PROMPT_SUFFIX="|"
@@ -14,7 +15,7 @@ VIRTUALENV_THEME_PROMPT_PREFIX='|'
 VIRTUALENV_THEME_PROMPT_SUFFIX='|'
 
 function prompt_command() {
-	PS1="\n${green}$(virtualenv_prompt)${red}$(ruby_version_prompt) ${reset_color}\h ${orange}in ${reset_color}\w\n${yellow}$(scm_char)$(scm_prompt_info) ${yellow}→${white} "
+	PS1="\n${green?}$(virtualenv_prompt)${red?}$(ruby_version_prompt) ${reset_color?}\h ${orange?}in ${reset_color?}\w\n${yellow?}$(scm_char)$(scm_prompt_info) ${yellow?}→${white?} "
 }
 
 safe_append_prompt_command prompt_command
diff --git a/themes/wanelo/wanelo.theme.bash b/themes/wanelo/wanelo.theme.bash
index 88d174014d..374c0ea7dc 100644
--- a/themes/wanelo/wanelo.theme.bash
+++ b/themes/wanelo/wanelo.theme.bash
@@ -1,13 +1,15 @@
-#!/usr/bin/env bash
-SCM_THEME_PROMPT_DIRTY=" ${red}✗"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓"
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
+SCM_THEME_PROMPT_DIRTY=" ${red?}✗"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓"
 SCM_THEME_PROMPT_PREFIX=" |"
-SCM_THEME_PROMPT_SUFFIX="${green}|"
+SCM_THEME_PROMPT_SUFFIX="${green?}|"
 
-GIT_THEME_PROMPT_DIRTY=" ${red}✗"
-GIT_THEME_PROMPT_CLEAN=" ${bold_green}✓"
-GIT_THEME_PROMPT_PREFIX=" ${green}|"
-GIT_THEME_PROMPT_SUFFIX="${green}|"
+GIT_THEME_PROMPT_DIRTY=" ${red?}✗"
+GIT_THEME_PROMPT_CLEAN=" ${bold_green?}✓"
+GIT_THEME_PROMPT_PREFIX=" ${green?}|"
+GIT_THEME_PROMPT_SUFFIX="${green?}|"
 
 RVM_THEME_PROMPT_PREFIX="|"
 RVM_THEME_PROMPT_SUFFIX="|"
@@ -18,9 +20,9 @@ function prompt_command() {
 	else
 		status=💔
 	fi
-	PS1="\n${yellow}$(ruby_version_prompt) ${purple}\h ${reset_color}in ${green}\w $status \n${bold_cyan} ${blue}|$(clock_prompt)|${green}$(scm_prompt_info) ${green}→${reset_color} "
+	PS1="\n${yellow?}$(ruby_version_prompt) ${purple?}\h ${reset_color?}in ${green?}\w $status \n${bold_cyan?} ${blue?}|$(clock_prompt)|${green?}$(scm_prompt_info) ${green}→${reset_color?} "
 }
 
-THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"$blue"}
+THEME_CLOCK_COLOR=${THEME_CLOCK_COLOR:-"${blue?}"}
 
 PROMPT_COMMAND=prompt_command
diff --git a/themes/zitron/zitron.theme.bash b/themes/zitron/zitron.theme.bash
index 7100052702..54272f11e6 100644
--- a/themes/zitron/zitron.theme.bash
+++ b/themes/zitron/zitron.theme.bash
@@ -1,9 +1,11 @@
-#!/usr/bin/env bash
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 # zitron theme by Florian Baumann <flo@noqqe.de>
 
 ## git-theme
 # feel free to change git chars.
-GIT_THEME_PROMPT_DIRTY="${bold_yellow}*${normal}"
+GIT_THEME_PROMPT_DIRTY="${bold_yellow?}*${normal?}"
 GIT_THEME_PROMPT_CLEAN=""
 GIT_THEME_PROMPT_PREFIX=""
 GIT_THEME_PROMPT_SUFFIX=""
@@ -18,7 +20,7 @@ function prompt_command() {
 	# user:host:pwd git-branch(*)$
 	# for example:
 	# noqqe:deathstar:themes master*$
-	PS1="${no_color}\u:$(hostname)${normal}:${bold_yellow}\W/${normal} $(git_prompt_info)${reset_color}$ "
+	PS1="${reset_color?}\u:$(hostname)${normal?}:${bold_yellow?}\W/${normal?} $(git_prompt_info)${reset_color?}$ "
 }
 
 safe_append_prompt_command prompt_command
diff --git a/themes/zork/zork.theme.bash b/themes/zork/zork.theme.bash
index 034b92054a..137059d03e 100644
--- a/themes/zork/zork.theme.bash
+++ b/themes/zork/zork.theme.bash
@@ -1,11 +1,14 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2034 # Expected behavior for themes.
+
 SCM_THEME_PROMPT_PREFIX=""
 SCM_THEME_PROMPT_SUFFIX=""
 
-SCM_THEME_PROMPT_DIRTY=" ${bold_red}✗${normal}"
-SCM_THEME_PROMPT_CLEAN=" ${bold_green}✓${normal}"
-SCM_GIT_CHAR="${bold_green}±${normal}"
-SCM_SVN_CHAR="${bold_cyan}⑆${normal}"
-SCM_HG_CHAR="${bold_red}☿${normal}"
+SCM_THEME_PROMPT_DIRTY=" ${bold_red?}✗${normal?}"
+SCM_THEME_PROMPT_CLEAN=" ${bold_green?}✓${normal?}"
+SCM_GIT_CHAR="${bold_green?}±${normal?}"
+SCM_SVN_CHAR="${bold_cyan?}⑆${normal?}"
+SCM_HG_CHAR="${bold_red?}☿${normal?}"
 
 #Mysql Prompt
 export MYSQL_PS1="(\u@\h) [\d]> "
@@ -22,23 +25,24 @@ esac
 PS3=">> "
 
 __my_rvm_ruby_version() {
-	local gemset=$(echo $GEM_HOME | awk -F'@' '{print $2}')
-	[ "$gemset" != "" ] && gemset="@$gemset"
-	local version=$(echo $MY_RUBY_HOME | awk -F'-' '{print $2}')
+	local gemset version
+	gemset=$(echo "$GEM_HOME" | awk -F'@' '{print $2}')
+	[[ -n "$gemset" ]] && gemset="@$gemset"
+	version=$(echo "$MY_RUBY_HOME" | awk -F'-' '{print $2}')
 	local full="$version$gemset"
-	[ "$full" != "" ] && echo "[$full]"
+	[[ -n "$full" ]] && echo "[$full]"
 }
 
 is_vim_shell() {
-	if [ ! -z "$VIMRUNTIME" ]; then
-		echo "[${cyan}vim shell${normal}]"
+	if [[ -n "$VIMRUNTIME" ]]; then
+		echo "[${cyan?}vim shell${normal?}]"
 	fi
 }
 
 # show chroot if exist
 chroot() {
-	if [ -n "$debian_chroot" ]; then
-		my_ps_chroot="${bold_cyan}$debian_chroot${normal}"
+	if [[ -n "$debian_chroot" ]]; then
+		my_ps_chroot="${bold_cyan?}$debian_chroot${normal?}"
 		echo "($my_ps_chroot)"
 	fi
 }
@@ -46,11 +50,11 @@ chroot() {
 # show virtualenvwrapper
 my_ve() {
 
-	if [ -n "$CONDA_DEFAULT_ENV" ]; then
-		my_ps_ve="${bold_purple}${CONDA_DEFAULT_ENV}${normal}"
+	if [[ -n "$CONDA_DEFAULT_ENV" ]]; then
+		my_ps_ve="${bold_purple?}${CONDA_DEFAULT_ENV}${normal?}"
 		echo "($my_ps_ve)"
-	elif [ -n "$VIRTUAL_ENV" ]; then
-		my_ps_ve="${bold_purple}$ve${normal}"
+	elif [[ -n "$VIRTUAL_ENV" ]]; then
+		my_ps_ve="${bold_purple?}$ve${normal?}"
 		echo "($my_ps_ve)"
 	fi
 	echo ""
@@ -58,12 +62,12 @@ my_ve() {
 
 prompt() {
 	SCM_PROMPT_FORMAT='[%s][%s]'
-	my_ps_host="${green}\h${normal}"
+	my_ps_host="${green?}\h${normal?}"
 	# yes, these are the the same for now ...
-	my_ps_host_root="${green}\h${normal}"
+	my_ps_host_root="${green?}\h${normal?}"
 
-	my_ps_user="${bold_green}\u${normal}"
-	my_ps_root="${bold_red}\u${normal}"
+	my_ps_user="${bold_green?}\u${normal?}"
+	my_ps_root="${bold_red?}\u${normal?}"
 
 	if [ -n "$VIRTUAL_ENV" ]; then
 		ve=$(basename "$VIRTUAL_ENV")
@@ -72,11 +76,11 @@ prompt() {
 	# nice prompt
 	case "$(id -u)" in
 		0)
-			PS1="${TITLEBAR}┌─$(my_ve)$(chroot)[$my_ps_root][$my_ps_host_root]$(scm_prompt)$(__my_rvm_ruby_version)[${cyan}\w${normal}]$(is_vim_shell)
+			PS1="${TITLEBAR}┌─$(my_ve)$(chroot)[$my_ps_root][$my_ps_host_root]$(scm_prompt)$(__my_rvm_ruby_version)[${cyan?}\w${normal?}]$(is_vim_shell)
 └─▪ "
 			;;
 		*)
-			PS1="${TITLEBAR}┌─$(my_ve)$(chroot)[$my_ps_user][$my_ps_host]$(scm_prompt)$(__my_rvm_ruby_version)[${cyan}\w${normal}]$(is_vim_shell)
+			PS1="${TITLEBAR}┌─$(my_ve)$(chroot)[$my_ps_user][$my_ps_host]$(scm_prompt)$(__my_rvm_ruby_version)[${cyan?}\w${normal?}]$(is_vim_shell)
 └─▪ "
 			;;
 	esac