Mothers and Other Strangers - S33-E9
Continuity mistake: A teenage Homer and his father travel to Utah to look for Homer's fugitive mother, whom they find. This completely contradicts the episode Mother Simpson, where Homer didn't reconnect with his mom until he was in his late thirties, and was told all his life by his father that she was dead, even believing that the grave of Walt Whitman belonged to his mother.
Continuity mistake: In the scene at the United Nations, the Russian placard is just a placard. In the next shot, the placard is attached with a rod to rotate it at the push of a button.
Homer's Triple Bypass - S4-E11
Continuity mistake: When we first see Krusty start talking to Homer, from the rear shot you can see Krusty is missing his pale colour on his face. However, in every other shot, his pale complexion is there. (00:15:10)
Homer's Triple Bypass - S4-E11
Continuity mistake: When we see Lisa in Sunday school, the colour chair she is sitting on changes from blue to brown as she talks about her dad being very sick. (00:14:40)
Other mistake: When Moe is running to the Simpsons' house there is a shot of him running past the moon. When running back to the bar, the same shot is used but is simply flipped. Note the house and rocks. (00:18:20)
Continuity mistake: When Moe confronts Jimbo, Jimbo has his back in a corner with just a cabinet behind him. When the shot changes he is next to the green chair. (00:19:00)
Continuity mistake: When Bart is out in the hallway being attacked by the wolf, he is missing his right shoe. When he goes into class he is missing his left shoe. (00:18:40)
Continuity mistake: When we see Krusty with a bird on his head, the claws' position on Krusty's head change. Note his left eye. (00:16:20)
Continuity mistake: Smithers opens the second case for Tom Jones as the green gas has all but dissipated from the case. When the shot changes, there is still gas coming from the case. The remaining gas also changes place in the vicinity of the case. (00:15:50)
Continuity mistake: When Tom Jones walks off-stage a towel appears around his neck instantly between instant camera cuts. (00:16:00)
Continuity mistake: When Burns is lay on the floor telling Smithers that he dreamed of Marge again last night, the painting behind Smithers is very badly painted and very childish in appearance. Burns' head is completely disproportionate for example. When the shot changes to Smithers the painting is now a lot more detailed and no longer looks childish. (00:14:42)
Itchy and Scratchy: The Movie - S4-E6
Continuity mistake: When Bart places his money on the kiosk, the end of the note is overhanging the edge of the kiosk. When he grabs his money after being refused entry, the entire note is on the kiosk. (00:19:20)
Itchy and Scratchy: The Movie - S4-E6
Continuity mistake: When Bart tries to buy a ticket to Itchy and Scratchy, the booth is unoccupied. When the shot changes the man has appeared in the booth. (00:19:20)
Tree House of Horror III: The Simpson's Halloween Special III - S4-E5
Continuity mistake: When Bart gets the Krusty doll, he pulls the pull string from the back of the doll. When the doll has finished talking, the pull ring has disappeared. (00:04:05)
Continuity mistake: When Krusty appears on stage he has a microphone that vanishes from his hands when he claps at the end of the song. (00:13:10)
Continuity mistake: When Homer comes into the kitchen to ask what 1 thing Lisa would want most, the milk carton and glass disappears from the table for a few shots. (00:07:10)
Continuity mistake: When Millhouse first spots the spookhouse, there is a red item on the floor by him, as he walks towards the spookhouse the item has gone. (00:03:00)
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.