Tree House of Horror VI - S7-E6
Continuity mistake: In "Attack of the 50 Foot Eyesores", the executive goes to the piano and you can see a penholder on his desk. But the camera angle changes to behind the piano in the next shot, the penholder has moved position and there are now more items on the desk.
Tree House of Horror VI - S7-E6
Continuity mistake: In "Nightmare on Evergreen Terrace", when the teacher hands out the papers before the test, you can see that in the desk sitting next to Bart is a student wearing green sunglasses and has blue hair. In the next shot, Martin is suddenly beside Bart.
Tree House of Horror VI - S7-E6
Continuity mistake: In "Nightmare on Evergreen Terrace", when Marge takes off her oven gloves you can see there is a plate beside her, but when she puts the gloves down in the next shot the plate has disappeared.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.