Continuity mistake: When the Stonecutters are singing "We do", the position of several characters, particularly Number 51 and Chief Wiggum, change randomly as the camera angles change. Number 51 starts at the end of the table on the right side, with Chief Wiggum two seats to the left of him. In later shots, Number 51, then Wiggum are both switched to the same position, midway up the left side. Then, when the song ends, Wiggum has disappeared, and Number 51 remains in this new position.
Homer Badman - S6-E9
Audio problem: When Bart and Lisa hug the T.V and Homer asks them if they are, they respond with "No". However, Lisa's mouth moves but you hear no sound.
Factual error: When you see Ned Flanders put the earth back inside the hole, he puts it back in much faster than is possible. In one shot, he is only just starting to put it back in, then you see Bart who talks to himself for a few seconds, then back to Flanders, who has finished burying what is later to be revealed as the plant that he (Ned) drowned.
Continuity mistake: In the scene where Lisa runs into the attic as she dives behind the chest she rattles a bird cage, later when Ned faints you can see that the bird cage has disappeared.
Tree House of Horror V - S6-E6
Continuity mistake: In 'Time and Punishment,' when the machine picks up the Simpsons' house, to take it to the 'Re-Neducation Centre,' the garage is on the wrong side of the house. It is on the correct side in the following shots of Homer returning. (00:11:20)
Continuity mistake: When Bart and Lisa are looking at the globe, Bart points out Argentina and 'Ran McNally.' 1) Next time you see the globe, it is showing Africa and Asia 2) Asia is shown incorrectly and 3) The equator has disappeared.
Continuity mistake: When Homer and Marge are on the plane, they both have seat belts on. However, when Marge gets up to run up and down the plane, both seat belts have disappeared.
Springfield Connection - S6-E23
Continuity mistake: When Homer first spots Snake dealing, you see Marge with a handbag. In the next shot, the handbag has disappeared.
Homer vs. Patty and Selma - S6-E17
Continuity mistake: When Marge says, "I wish you wouldn't put Homer down like that.", Patty and Selma's dresses swap colour between shots.
Homer vs. Patty and Selma - S6-E17
Continuity mistake: When one of Marge's sisters says, "He blew all your savings on jack o'lanterns.", one of the armrests on the sofa is black for some reason.
Homer vs. Patty and Selma - S6-E17
Continuity mistake: When Homer for the second time throws out Patty and Selma, the knocker just stays in the same place as if the door hasn't opened at all. (It looks like it is floating in mid-air).
Lisa on Ice - S6-E8
Continuity mistake: When Lisa throws her academic alert into the trash, she jumps half way across the stage without taking a step.
Springfield Connection - S6-E23
Continuity mistake: When Marge is making celery soup, The Front view of her shows just the chopping board in front of her. Then when Lisa talks to her the microwave is seen in front of her.
Tree House of Horror V - S6-E6
Audio problem: In 'The Shinning' when the Simpsons finally arrive at the house, they climb out the car and start yelling "Hi." and "We're here." Listen to Lisa's voice, and watch her mouth. The audio is totally out of sync with her mouth movements. (00:02:30)
Revealing mistake: When Bart is watching Rod and Todd walk over to Ned Flanders, you can see their reflections on Bart's telescope. Their reflections do not match their actual positions.
Springfield Connection - S6-E23
Continuity mistake: When Marge is reading the books on death sports the police arrive and she turns around, you can see the two posts with the round balls on top with no words on it. But when Marge starts walking towards the police station it says "Police" on the balls and the post changes size. Also the door to the police station changes from brown to blue to clear glass and back to blue during the scene.
Tree House of Horror V - S6-E6
Continuity mistake: In 'Time and Punishment,' when Homer exits the basement, he discovers Bart and Lisa are giants, and he then screams and runs back to the "basement" - however the same door that leads to the basement seconds ago, now leads to a green -carpeted room, and the basement seems to have vanished. The door is also hinged on the wrong side. (00:12:50)
Homer vs. Patty and Selma - S6-E17
Continuity mistake: When Homer tries to tell Marge how he did in the test, Selma and Patty are holding their cigarettes. In the next shot, the cigarettes are in their mouths.
Continuity mistake: When the Simpson family and Jay Sherman are having dinner, things like the food from their plates, their knives and forks and even Homer's burping trophy disappear and then reappear for a couple of seconds before disappearing again.
Tree House of Horror V - S6-E6
Continuity mistake: In 'Time and Punishment,' Homer goes back in time, then returns, and the kitchen table has plates of food, cutlery and glasses all set out. Then when Homer is informed that Ned is the Lord of the Universe, the house starts shaking, but you can see the table is now totally clear. (00:11:15)