Continuity mistake: While Homer and Barney are smoking in the boys bathroom, when Principal Dondelinger walks in on them the "boys" sign on the exterior side of the door disappears in the closeup, but the sign reappears as Dondelinger exits. The door push plates on both sides of the swing door also vanish/reappear during the scene. (00:04:35)
Continuity mistake: When Homer shows up to the Bouvier home the night of the prom, Selma and Patty open the door and it opens outward, but in the following shots the door has been opened inward. (00:16:10)
Continuity mistake: When Homer stands outside the Bouvier house to pick up Marge, the home's front door has three diagonal windows from upper left to lower right. However, when Marge gets home later after the prom, the three windows are diagonal the opposite way from upper right to lower left. (00:16:10 - 00:21:00)
Continuity mistake: When Marge comes downstairs she's shocked to see Homer in her house, and when the doorbell rings we see Mrs. Bouvier wearing an orange belt with a red buckle, but then the colors switch to an orange buckle and the belt center is red. (00:16:45)
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.