Non-canonIn Treehouse of Horror III a zombified George Washington can be seen walking around Springfield Elementary School. Homer kills him again with his shotgun.
As George Washington is deceased most of his appearances are minor or in flashbacks or mentions during the series. George Washington appears in Treehouse of Horror episodes. such as in Treehouse of Horror III, He appears as a zombie walking around Springfield Elementary School. Where he is killed by Homer Simpson.
At the end of Frinkcoin, Mister Burns has a dream about dancing with him. George says Burns' looks familiar and asks if he fought alongside him in "the war". Burns affirms he was in the war (the American Revolution) but that they weren't on the same side.