Continuity mistake: The moss on Walt Whitman's grave when Homer removes it changes.
Much Apu About Nothing - S7-E23
Continuity mistake: When Willy is threatening the children and Skinner it shows that Lisa has her hands on her sides and she is holding nothing. In the following shots, she has a blue book held against her chest.
Much Apu About Nothing - S7-E23
Continuity mistake: When the mob return to Quimby his assistant's clipboard changes colour between shots.It goes from light brown to burgundy then back to light brown again.
Continuity mistake: When Homer starts the song at the end of the episode, the doors to the house behind him are open. In the next shot of the house they are closed, then they are open again in the next shot.
Continuity mistake: After Bart finds out that Lisa took the teacher's books, his Hall Monitor sash disappears and reappears for several shots. (00:20:05)
Itchy and Scratchy: The Movie - S4-E6
Continuity mistake: When Homer is in Lisa's classroom and imitates a farting sound, there is a sink at the back of the classroom and nobody is using it. However in the wide shot, there are suddenly two people by the sink. When the shot is back to Homer, nobody is by it. (00:03:00)
Like Father, Like Klown - S3-E6
Continuity mistake: At the end of Krusty's story, Homer changes from being in his tuxedo to being in his normal clothing. (00:10:10)
Suggested correction: It should be noted that a considerable amount of time has passed while Krusty is telling his story. Note the candles in the screenshot for example, they have burnt out during the story. Its reasonable to assume that there would have been a chance for them to change during this time.
Continuity mistake: When the wolf runs out of Krusty's studio, the woman who described it changes from having two gloves on to one glove on. (00:16:40)
Continuity mistake: After Krusty is done doing the special promotion commercial, he is given a telegram informing him of the Soviet boycott. However, this is a flashback, and at this point in time Krusty is illiterate (as will later be established in season 1) so he shouldn't be able to read the telegram. (00:12:30)
Continuity mistake: Bart turns the door handle to the joke shop and a boxing glove comes out through the door and hits him. But when he opens the door there is nothing on the other side for the glove to come out of.
Home Away From Homer - S16-E20
Continuity mistake: When Homer meets Coach for the first time (and maybe another point in the episode), the position of Ned's house's window frames to the side of the door change between shots.
Continuity mistake: Bart and Homer escape from the court by jumping out of a window, however in the next shot they are running away from the door as if they escaped via the doors.
Continuity mistake: When Edna sits at her desk saying "Oh, Woodrow. How could you stand me up?" the clock reads 3 O'clock. Seconds later, as Bart talks with Edna, the clock reads 4 O'clock. (00:16:45)
Continuity mistake: In the scene where the Simpsons are sitting down to eat dinner, we see Bart pour tomato ketchup all over his potatoes. Then when the shot changes, we can see all the ketchup bottle and the corn has disappeared, and the ketchup has come off his plate. (00:04:50)
Bart Carny - S9-E12
Continuity mistake: Up until the point at which Skinner starts throwing rings at the block in front of the Spanish lamp, the block simply doesn't exist. It only appears once he starts throwing the rings.
The Simpson's 138th Show Spectacular - S7-E10
Continuity mistake: During the false ending to "Who Shot Mr. Burns: Part 2", Smithers moves position when Burns explains what happened.
Continuity mistake: The antenna from Homer's car disappears when he drops Mother Simpson at the gas station.
Continuity mistake: When Bart arrives at school in the bus, after Homer plowed the road for the bus, the sidewalk is covered in snow except for Martin's footprints. Then, when he gets out, the sidewalk has been shovelled, as there is no snow on it. Following this, Bart is pelted by snowballs, which sends him falling face-first into the sidewalk, which is once again covered in snow. (00:10:20)
Diatribe of a Mad Housewife - S15-E10
Continuity mistake: When Homer comes home in the Ambulance we can see there is a yellow logo on the back passenger door. In one shot it randomly disappears. (00:05:40)
I, (Annoyed Grunt)-bot - S15-E9
Continuity mistake: In this episode it is shown that Snowball I is buried in their backyard, but in other episodes, notable the one where Sideshow Bob becomes mayor, it is established that she is buried in a pet cemetary.