R2-D2 is a character from Star Wars who occasionally appears throughout the show. Apu goes in a costume of R2-D2 at Halloween [1]. He next appears in a commercial for the Bi-Mon-Sci-Fi-Con, in a tag team wrestling match watching his counterpart C-3PO being demolished by two robotic troopers from Battlestar Galactica. He also appeared in Bart's daydream of his Moon Party that he would have with $1,000 [2].
Appearances
THOH – "Treehouse of Horror XVI" 
Episode – "The Regina Monologues" - Episode – "Mayored To The Mob"
Episode – "You Kent Always Say What You Want"