There's No Disgrace Like Home - S1-E4
Revealing mistake: When the Simpsons are eating at the dinner table, Marge's necklace keeps flashing white.
Revealing mistake: When Bart makes a copy of his photo for Lewis, footage of Milhouse inserting a coin into the copy machine is used. You can see Milhouse's pink shirt sleeve instead of Bart's orange shirt sleeve. This same shot is again reused a third time seconds later. (00:09:55)
Continuity mistake: During the theater scene, the man in the back with the moustache and green jacket watching the Space Mutants movie changes from having yellow skin to brown skin after Bart blows a raspberry. (00:09:30)
Revealing mistake: The blonde woman's midriff (from the Space Mutants movie) flashes pink for a frame.
Continuity mistake: When Bart returns home while Lisa is watching Krusty, the door opens without Bart even touching it. (00:22:00)
The Mook, the Chef, the Wife, and Her Homer - S18-E1
Revealing mistake: When Fat Tony says "The Calabresis. My archenemies in waste management." while driving the carpool, a huge line briefly appears around his cheek and mouth.
Marge Simpson in 'Screaming Yellow Honkers' - S10-E15
Continuity mistake: When Eddie the cop (as Curtis E. Bear) is being bludgeoned with 2x4's at traffic school, Krusty's nose is the same color as his skin instead of being red.
Wild Barts Can't Be Broken - S10-E11
Continuity mistake: When Wendell is among the kids seen inside the police van, his skin is a lot less pale than usual.
Revealing mistake: When Fat Tony says,"I am not so much disappointed as I am blinded with rage", the dark circles under his eyes disappear for a split second.
Continuity mistake: When Kent Brockman gives his after thought on Lisa's speech, his hair and clothes have changed colors.
Homer's Barbershop Quartet - S5-E1
Continuity mistake: Homer and Marge's bedroom has photos of Bart and Lisa when they were 10 and 8 years old. However, the story takes place when Bart and Lisa were only 3 and 1. (00:12:00)
El Viaje Misterioso de Nuestro Homer (a.k.a. The Mysterious Voyage of Our Homer) - S8-E9
Continuity mistake: When Homer is freaking out and starting to hallucinate after eating a few peppers, Jasper is behind a tent stall when Homer is running away from Ned Flanders, but just seconds later when Homer falls to the floor, Jasper is in front of Homer. (00:08:05)
A Midsummer's Nice Dream - S22-E16
Continuity mistake: The seating arrangements during the Cheech and Chong show keep changing between shots. Smithers is first seen sitting between Patty and Luigi, then he is between Louie and Legs, and then he is between Patty and Luigi again, then finally, he is sitting next to Mr Burns. And Miss Hoover is at first two rows in front of the Simpsons, then she is a row behind them when Homer is going to the stage.
Continuity mistake: At one point when Homer is giving his speech in front of the Jebediah Springfield statue, Carl's skin is yellow. In all other shots he is back to his normal color.
Continuity mistake: At one point, while everyone is clapping for Homer during the debate in The Town hall, Apu is seen with yellow skin, and Chief Wiggum is seen with black hair among the townspeople. In all other shots, they're back to their normal skin and hair color.
Grade School Confidential - S8-E19
Continuity mistake: Edna Krabappel's name on the envelope is misspelled as "Enda" when Bart is opening and reading the letter, but is spelled correctly when viewed in close-up.
Scenes From a Class Struggle in Springfield - S7-E14
Revealing mistake: When Lisa is first shown riding the horse, the horse's eye is colored solid red.
Continuity mistake: When Moe tries to convince Dr Hibbert that Moe's is a family restaurant, Carl's skin is yellow.
I'm Goin' to Praiseland - S12-E19
Continuity mistake: When the citizens are leaving the park in disappointment, Manjula walks past the screen and has yellow skin, light brown hair and is wearing a blue dress. In the next shot she is back to her normal skin color and is wearing her usual pink dress.
Revealing mistake: During Skinner's speech to the students in the school cafeteria, two Allison Taylors are seen sitting on different sides of the cafeteria.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.