Continuity mistake: When the Shelbyville kids drop the basket of lemons when Bart and friends start throwing lemons at them, the position of the basket changes when the Shelbyville kids run off. Note the colour of the Springfield grass and the Shelbyville grass.
Continuity mistake: When Marge says good night to Bart he has pyjamas with sleeves on. Then when he puts on Lisa's nightgown (which doesn't have sleeves) to make Marge think he is Lisa, Bart's pyjama sleeves can't be seen under Lisa's nightgown. (00:12:25)
Continuity mistake: During the 20 years ago flashback, when Maude goes to spray water on Homer's pants, she is sitting on a tree in the background. When Homer and Marge talk, she doesn't spray water on his pants, but in the next shot she is gone. (00:17:35)
Tree House of Horror XI - S12-E1
Continuity mistake: In the "Scary Tales can Come True" segment, Bart's plague rat bite disappears for the rest of the segment.
Continuity mistake: During Lisa's and Bart's segment, time seems to run really quickly. When Lisa leaves West Springfield Elementary it is 11:00 and when she gets to Moe's it is noon, then a few minutes later it is 2:50. When Bart and Milhouse find Fat Tony it is noon, then when Bart gets hit by the truck, it is almost 3:00.
Continuity mistake: When Bart goes up to his treehouse to write the kidnap letter, he throws his Murder 4 Life jumper out the treehouse entrance. Later, when Lisa finds the jumper, it is now on a tree branch as if he threw it out of one of the treehouse windows.
Diatribe of a Mad Housewife - S15-E10
Continuity mistake: When Homer goes to Ned to make sure Marge imagines nothing again, Homer puts his hand through the door, then he puts his hand through the mailbox, then Nelson puts his hand out to steal the doormat. Nelson puts his hand just over the mailbox, then in the next shot when it reveals Nelson is there, his hand is suddenly under the mailbox without enough time to move it.
Sideshow Bob's Last Gleaming - S7-E9
Continuity mistake: When Homer drives under the plane to save Bart from Sideshow Bob, you can see he drives under the plane twice.
Thirty Minutes Over Tokyo - S10-E23
Continuity mistake: When Lisa gets the tickets on the "volcano", she is a few inches away from the end of the bridge. When it falls and Marge runs onto the bridge, she is now in the middle of it.
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: 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: 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 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: 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: When Homer and Ned attempt to escape from their Vegas wives at the buffet. The Vegas Wives are directly in front of them, when Homer runs off he runs in an opposite direction, nowhere near them. When Homer runs out, the Vegas wives are right next to him.
Tree House of Horror IV: The Simpson's Halloween Special IV - S5-E5
Continuity mistake: When Otto hits Hans Moleman's car, it has a number plate on it, which disappears when he crashes. (00:10:40)
Tree House of Horror IV: The Simpson's Halloween Special IV - S5-E5
Continuity mistake: Just before Homer is sucked into Hell, he is wearing pyjamas. When he's in Hell, he's wearing his usual day clothes. (00:04:10)
Continuity mistake: Milhouse shows Lisa a laptop with e-mails on it. There is also a shot with a list of the e-mails. At no point does anyone click anything, but the next shot shows a different page on the laptop.
Continuity mistake: In the scene where Smithers is showing Burns the bar, Smithers is in his grey suit. When Burns turns to talk to Grizzly Shaun, Smithers is wearing his standard green jacket and bow tie. Afterwards he is back in his grey suit.
Continuity mistake: During the scenes at the site of the mall during the part where they find the Angel, Skinner's hat disappears and reappears.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.