Treehouse of Horror XX Episode Number Production Code Original Airdate Blackboard Text Title Screen Billboard Couch Gag Special Guest Voices Show Runner(s) Written By Directed By Credits For the continuing series of Halloween specials, see Treehouse of Horror Series. “As a vegetarian, I did not eat any tainted burgers. And as a convenience store owner, I'm armed to the teeth.” ―Apu Nahasapeemapetilon"Treehouse of Horror XX" is the fourth episode of Season 21 and the twentieth Treehouse of Horror episode.