Darlene is a background character that has appeared in multiple episodes, although she had minimal speaking lines. One of her first appearances was in "Attack of the Saucer Morons", where she appeared among the Saucer Morons who worshipped Zim when his disguise was discovered. She also appeared as a bystander in Zim's yard in "The Girl Who Cried Gnome".
She was given a name as well as a voice in "Mortos der Soulstealer" when Mortos met her at a carnival, which she was shown to be working at. Her only speaking lines in this episode were "Hi" and "All right", both uttered in a very shrill voice. Despite numerous other cameos in episodes, very little else is known about her.
Mortos seemed to have a crush on her, although their relationship could not be explored far, as he had to soon depart back into his realm.