The Old Man and the Lisa - S8-E21
Continuity mistake: When Mr Burns is looking at the Ketchup and Catsup bottles in the supermarket, there is nothing in front of him but in the next shot his trolley appears from nowhere.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Smithers tells Mr Burns to "maintain your dignity", you can see there is a cup, plate and spoon on the table. In the next shot, all three items have disappeared.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Lenny is sitting at Mr Burns' desk, you can see there is nothing in front of him on the table, but in the next shot a "Lenny" name card appears.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Smithers tells Mr Burns that his money has gone, you can see there is nothing on the blue pad on the table, but in the next shot two fountain pen holders have appeared.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Principal Skinner is at the Recycling Centre, you can behind him there are steel drums but in the next shot they have changed to newspapers.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Mr Burns is speaking to his lawyers in his office, there is a blue pad on the table that keeps disappearing and re-appearing between shots.
The Old Man and the Lisa - S8-E21
Continuity mistake: When we see Mr Burns speaking to his lawyers, you can see there is a book stand on the table, but in the next shot it has gone.
Continuity mistake: During a shot of everyone at church, Carl is seen with a red sweater, after Homer says "Dammnit!", Carl's sweater turns blue.
Continuity mistake: In the cafeteria at the power plant, in the wide shot the clock on the wall is on 9.00, but closer up it's showing 10.35.
Continuity mistake: The hole in the wall made by the acid changes shape and size in several scenes.
Continuity mistake: Lenny says that Homer got his job by showing up when the nuclear plant was opened. In the episode "I Married Marge" (Season 4), the plant is already open when Homer interviews for a position, doesn't get it, then works at Gulp 'N' Blow.
Continuity mistake: After Milhouse explains to Bart how the warehouse collapsed, he appears to be bald for some reason.
Simpsons Spin-off Showcase - S8-E24
Continuity mistake: In Moe's spin-off, just before Barney leaves the bar, his beer glass vanishes.
Simpsons Spin-off Showcase - S8-E24
Continuity mistake: In the beaver sketch, "Lisa" is holding Maggie in front of her to show everyone her first tooth. In the next shot, Maggie is instantly to her side.
The Secret War of Lisa Simpson - S8-E25
Continuity mistake: When Lisa and Bart are practising for the 'Eliminator', Lisa doesn't have a rope round her waist, but when she falls she does.
The Secret War of Lisa Simpson - S8-E25
Continuity mistake: When Lisa climbs to the top of the Eliminator, there is a platform for her to stand on. Strangely in the next shot Lisa is standing on nothing so she appears to be standing in mid-air.
The Secret War of Lisa Simpson - S8-E25
Continuity mistake: The vehicle they are driving changes form when they drop off Bart at military school to when they drive home. They leave with Homer's purple car (obvious from the crumpled headlight) and as they leave the military school it's Marge's orange car (obvious from the ski racks and lack of a trunk). It's clear from the entire scene that this is all one trip.
The Secret War of Lisa Simpson - S8-E25
Continuity mistake: When Lisa has just been saved from falling, from the Eliminator at night, three boys approach. The two boys on the right swap positions between shots.
The City of New York vs. Homer Simpson - S9-E1
Continuity mistake: Just before Homer tries biting off the boot, he is wearing a watch. But from then on it disappears off his arm until he is trying to figure out how many hours it is from 9-5.
The City of New York vs. Homer Simpson - S9-E1
Continuity mistake: When the camera pans down the Trade Center, there is no washing line there. But a few shots later, a washing line appears.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.