Continuity mistake: The card Bart has written for Milhouse is blank inside. However when Lisa looks at the card, the pun of the joke (on The Front of the card) is now there. (00:01:15)
Continuity mistake: When Comic Book Guy turns off the water hydrant, the two boys in purple and blue trunks change position between shots.
Bart Carny - S9-E12
Continuity mistake: When the Simpsons drive up to the house, there are no boards on the window. When they can't get in, suddenly there are boards on the windows.
Treehouse of Horror XV - S16-E1
Continuity mistake: When Maggie crawls out of the stroller and into the capsule, the stroller has no harness, but when Marge sees the empty stroller, there is a harness.
How Lisa Got Her Marge Back - S27-E18
Continuity mistake: The pictures of the celebrities behind Lisa and Andrew Rannels change position depending on the whether scene is focusing on Lisa or Andrew.
Two Cars in Every Garage and Three Eyes on Every Fish - S2-E4
Continuity mistake: When Marge is standing outside the Kwik-E-Mart, she is holding some papers with a picture of Mary Bailey and the words "Re-Elect Bailey." But in a long shot of Marge in the next shot, the papers she is holding in her right arm are now completely blank.
Some Enchanted Evening - S1-E13
Continuity mistake: When Ms Botz is leading Bart, Lisa and Maggie to the living room, the video she is carrying in her hand is brown. In the next shot, it is now blue, and when she is talking to Bart, it is brown again.
Tree House of Horror VII - S8-E1
Continuity mistake: In Citizen Kang, when Homer bursts in at the Dole-Clinton Debate, you can see the wall behind him is light blue, but when we see a close-up of Homer, the wall is now brown.
Continuity mistake: When the Simpsons are at the restaurant at the start, Bart has no medal on his jacket. But when Lisa remarks a few seconds later that Homer gave Bart a medal, one has appeared on his jacket.
Continuity mistake: When Stefan starts crying at the football, Marge puts some music on and Homer's Sadgasm band appears on the radio. At this point, Stefan's wine glass is in front of the couch on the floor. Stefan then says he needs whale songs - Marge puts an "Oceans of the Sea" CD in the CD player and the wine glass in front of the couch suddenly vanishes.
Continuity mistake: The house is ripped from its foundations, but later on when it falls down the waterfall you can see the floor is completely intact.
Continuity mistake: When Homer gets out of the electric chair, the sponge has disappeared from on top of his head.
Eternal Moonshine of the Simpson Mind - S19-E9
Continuity mistake: Near the end, when Homer says "I'm a genius", Krusty is seen with yellow skin, but is later seen with his usual white skin.
Continuity mistake: When Marge enters "Your home from space" the address is still http://www.google.com, then the shot changes to Marge outside and then shows the computer again where the address is now http://yourhomefromspace.com.
How Munched is That Birdie in the Window - S22-E7
Continuity mistake: Right before the Itchy and Scratchy Show episode starts, Santa's Little Helper is colored in a much darker shade of brown than usual.
Continuity mistake: When Bart says "Stop feeling sorry for him", Dr. Robert Terwilliger Sr. is seen sitting in the audience, even though he is supposed to be sitting in the witness stand.
Continuity mistake: When the jury is "oohing" Wallace Brady, Lenny's five o'clock shadow is missing. It reappears in the next shot.
Continuity mistake: Milhouse's hair is blonde in the school bus' mirror reflection.
Realty Bites - S9-E9
Continuity mistake: While Homer is driving Snake's car, he passes a place called Heinrich's Monocle Shop three times.
Brother From Another Series - S8-E16
Continuity mistake: Sideshow Bob and Cecil's glasses keep switching from wine glasses to champagne glasses while they are having dinner.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.