Treehouse of Horror XV - S16-E1
Continuity mistake: At the beginning when Kang and Kodos's boss comes to have dinner, his stomach explodes leaving a hole, yet in the next shot the hole has vanished. (00:00:40)
Treehouse of Horror XV - S16-E1
Continuity mistake: Ned hammers in the For Sale sign; a few shots later, when Homer comes, it is no longer there. (00:03:40)
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.