Plot hole: In a flashback, Agnes Skinner blames Seymour for costing her a gold medal in the 1952 Olympics by kicking her while in her womb. This couldn't have been that Seymour Skinner since he was revealed to be an imposter earlier in the series. It would have been the other Seymour who returned from Vietnam who cost her the gold medal.
Plot hole: Warren's (as Bob) face falls off and tries to hold it with his hand. When he appears in the next scene, his face is totally sealed with nothing to seal it with. (00:16:25 - 00:17:55)
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.