Continuity mistake: When Frink collapses at the table, his sleeves are green. When it cuts to a wide shot, they are yellow.
Continuity mistake: When Bart and Lisa are in the compound, just before Bart gets brainwashed, the bags that were behind Lisa disappear. Homer and Marge were on the other side of the room, so they couldn't have picked them up.
Continuity mistake: At the Model U.N. meeting, Bart finishes speaking and puts down his papers on the right hand side of his desk. Two shots later, the papers are on the middle of the desk. (00:03:10)
Continuity mistake: The pens and pencils in the good butter change between shots when Homer begins his website. (00:04:55)
Continuity mistake: In the shot before Nelson says "Hey, Simpson. Race you", Ralph is seen sitting on the row in front of Martin. But when Ralph says "Go, banana" he is suddenly sitting two rows in front of Martin. (00:05:25)
Continuity mistake: The part of the bus that got a hole in causing it to sink changes position when Bart goes to get the cooler later. (00:07:10 - 00:12:20)
Continuity mistake: When the kids wash up on the island, Lisa, Wendell, Martin, Lewis and Sherri are on land and Bart, Milhouse, Ralph, Nelson and Terri are still in the water. In the next shot, Bart, Milhouse, Ralph, Nelson and Terri are on land with the others. (00:07:15)
Continuity mistake: There are 10 kids stuck on the island. But after the kids have washed up on the island and it cuts to the wide shot and it shows them on the beach, there are only 6 kids. (00:07:20)
Continuity mistake: Just before Bart mentions the Swiss Family Robinson, Lewis is standing in front of him. When Bart mentions the Swiss Family Robinson, Lewis moves further back without enough time for him to move. (00:07:50)
Continuity mistake: A fire is started when Milhouse's glasses are used by Nelson. But when Nelson hands Milhouse back the glasses in the next shot, the fire has disappeared. (00:11:40)
Continuity mistake: As soon as the fish bites Bart's butt and causes a rip in his shorts, the rip disappears almost instantly. (00:12:40)
Continuity mistake: When Bart comes out of the water with the cooler, he doesn't have a shirt on. At no point does he put his shirt back on, it reappears when Lisa takes the food off everyone. (00:12:45)
Continuity mistake: Everyone discovers Milhouse ate the food so they walk up to him. The shot cuts and they are further away than they were in the previous shot. (00:13:50)
Continuity mistake: At the trial, Milhouse moves over to Lisa and Bart is in the middle of them. In the next shot, Bart has disappeared. (00:15:25)
Continuity mistake: At Milhouse's trial on the island, Milhouse moves to Lisa so he is at least a foot away from her. In the next shot, Milhouse and Lisa are standing right next to each other. (00:15:25)
Continuity mistake: When Bart, Lisa and Milhouse are running away from the others, the order is Bart, then Lisa, then Milhouse. In the next shot it is Lisa, then Bart, then Milhouse. (00:18:45)
Continuity mistake: Bart, Lisa and Milhouse run away from the others and are stopped by a cliff. Milhouse then grabs onto a vine which was never there in previous shots. (00:19:00)
Continuity mistake: When everyone is running out the cave after finding the boar, Wendell's skin is yellow instead of his usual pale white. (00:19:50)
Continuity mistake: Whilst everyone is eating the boar, they are noticeably moving. But when it cuts the final wide shot, no-one is moving an inch.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.