Wallscrawl

"Wallscrawl" was the name given to the Kang drawings on the walls of Paradise Towers. They depicted diverse objects and themes, including the cleaners. One of the Caretakers' tasks was removing wallscrawls. They called the Kangs "wallscrawlers".

After Pex sacrificed himself to kill Kroagnon, a wallscrawl visible when the Doctor's TARDIS dematerialised stated "Pex lives". (TV: Paradise Towers)