Marge vs. the Monorail - S4-E12
Continuity mistake: The Springfield forest is across the road from the school, but in many other episodes, it is somewhere completely different.
Marge vs. the Monorail - S4-E12
Continuity mistake: Mayor Quimby's suit changes from dark blue to purple throughout the whole town hall scene.
Marge vs. the Monorail - S4-E12
Continuity mistake: When Grandpa Simpson stands up in The Town hall, the position and amount of paintings on the wall change several times between shots. (00:06:10)
Marge vs. the Monorail - S4-E12
Continuity mistake: Throughout the whole town hall scene, people constantly change positions between shots.
Marge vs. the Monorail - S4-E12
Other mistake: Lanley's desk in his trailer suddenly gets brighter even though none of the lights in the trailer were turned on. (00:12:50)
Marge vs. the Monorail - S4-E12
Continuity mistake: Cobb's hair in North Haverbrook changes length between shots. (00:14:10)
Marge vs. the Monorail - S4-E12
Continuity mistake: When celebrities are coming to ride the monorail, the positions of people in the crowd changes positions between shots.
Tree House of Horror III: The Simpson's Halloween Special III - S4-E5
Plot hole: At the theatre in the "King Homer" bit, the audience are treated to a traditional showgirl spectacle. But the girls have no curtain behind them, and so the audience should have seen Homer the ape, but they act completely surprised a minute later when Homer comes on. (00:11:40)
Revealing mistake: When Lisa says "Truly this was an act of God", her ear disappears and reappears several times. (00:19:30)
Factual error: When Selma throws Moleman out of her car, the passenger door is hinged at the rear instead of The Front as it should be on a relatively-modern hatchback, and the window crank is visible on the outside of the door.
Revealing mistake: Part of Homer's right arm flashes white when he asks his father for $15,000. (00:08:50)
Kamp Krusty - S4-E1
Continuity mistake: When Lisa is reading her report card, the writing suddenly appears on the back of the paper, even though she didn't flip the card. (00:04:10)
Marge vs. the Monorail - S4-E12
Revealing mistake: When the passengers board the Monorail, Homer begins pushing two buttons. The second button he pushes is just the counter. There is no button there. (00:15:40)
Marge vs. the Monorail - S4-E12
Continuity mistake: When Quimby states to Lyle that Springfield is twice as smart as Shelbyville, Quimby lowers his gavel at the end of the line. In a sudden close-up of Quimby, his gavel is raised again. (00:07:05)
Continuity mistake: When Roger Meyers throws his nameplate at the writer the second time, the animation is repeated from when he threw it at him earlier. It's more obvious because his mouth doesn't match what he's saying and the background is orange instead of purple like the rest of the scene.
Brother From the Same Planet - S4-E14
Revealing mistake: The shot of Homer saying "Marge, when kids say bad these days, they mean good. And to shake your booty means to wiggle one's butt" is recycled from the opening scene from Life on the Fast Lane. Notice the animation is of a much lower standard than the rest of the episode.
Marge vs. the Monorail - S4-E12
Continuity mistake: Doctor Hibbert was among the passengers on the monorail on the first ride, but he is seen with a pair of conjoined twins in his office soon after.
Revealing mistake: When Homer points at the donut guy, his right shirt cuff is colored yellow. (00:12:50)
Revealing mistake: Krusty's nose flashes white for a split second during his song for the winner of the Little Miss Springfield pageant. (00:15:06)
Tree House of Horror III: The Simpson's Halloween Special III - S4-E5
Audio problem: In "Clown Without Pity" when Homer yells "The doll is trying to kill me, and the toaster's been laughing at me!" his mouth doesn't move. (00:06:45)
