Groening has appeared in the series before, but not in a speaking role. His previous appearances have included the placing of a framed photo of him in Comic Book Guy's store, where Groening is banned for life.
In Sunday's episode, "My Big Fat Geek Wedding," Principal Skinner backs out of his planned wedding to teacher Edna Krabappel -- who rebounds into the arms of Comic Book Guy. He takes her to a Sci-Fi convention, where they run into Groening at a celebrity autograph session.
As Fox prepares for the show's upcoming 16th season, the New York Times reported Wednesday that the show will not produce its normal season of 22 episodes because of delays caused by a contract holdout by voiceover actors. Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith, Hank Azaria and Harry Shearer -- who currently earn about $125,000 an episode -- are reportedly demanding $360,000 an episode and a percentage of the show's profits.