Tree House of Horror X - S11-E4
Continuity mistake: While the Simpsons are standing in the line, waiting to enter the rocket to Mars, you can see Professor Frink wearing a white shirt. However when he enters the lift to the rocket, he has a green shirt on.
Continuity mistake: When wedding has been just called off, Lunch Lady Doris calls everyone for wedding cake, and among people who rush to it we can see Moe (you can recognize him by his eyepatch), then, Lisa starts to walk off and among the people she passes by you can see both Lunch Lady Doris and Moe.
Continuity mistake: In the White House, Bart puts his cassette player front towards Lisa, but when Lisa pushes it out, it switches to face Bart between shots.
Homer's Triple Bypass - S4-E11
Continuity mistake: When, Lisa bangs on the window of the operating theatre, there is a person sitting behind her who is asleep. However, when she shouts to Dr Nick, the people behind her are completely different. Then she sits down again, and the sleeping person is behind her. (00:20:00)
Homer vs. the 18th Amendment - S8-E18
Continuity mistake: When Homer and Bart are escaping from the cops after stealing kegs of beer from the dump, they drive through a cemetery and slam into a headstone, breaking the right headlight of the car. When they pull into the driveway back at Evergreen Terrace, the left headlight is the broken one.
Home Away From Homer - S16-E20
Continuity mistake: As the Simpsons are in the cinema watching "Kosovo Autumn" you can see there is a seat next to Homer to the right of screen. When Homer starts complaining about the film but cannot leave because he is stuck in his seat, the shot changes and we see him from behind however the seat that was next to him has disappeared.
Continuity mistake: The lock only appears on the door when Marge uses it. (00:14:45)
Continuity mistake: When Lisa is watching tapes of Francine's bullying, there is a scene where they are at the pool. Francine is wearing nose clips in this scene. But when Lisa freeze-frames and leans in to closer inspect the shot, Francine's face is shown on the screen without nose clips. They appear again when Lisa exclaims "Of course. The nose clips."
Continuity mistake: When Bart is eating the grubs, his tongue appears to be green, in all other shots it's back to red.
$pringfield (or How I Learned to Stop Worrying and Love Legalized Gambling) - S5-E10
Continuity mistake: As Marge arrives home and sees the bullet holes in the door, the shot changes to a POV shot from behind the door and you can see there are some changes in the holes. The first change is there are three bullet holes on the right hand side which are all the same distance from each other, when she enters the middle hole has moved closer to the bottom one. The other change is the large hole in the middle of the door. On the bottom right hand side its shape goes from being a little irregular to a more round shape. (00:16:20)
Home Away From Homer - S16-E20
Continuity mistake: When Coach is cutting down trees he tells Homer that he borrowed some petrol (or 'gas' in America) from his car, and the shot goes to his car. However when Homer runs indoors the car has vanished.
Burns Verkaufen der Kraftwerk - S3-E11
Continuity mistake: When Mr Burns is bowling outside with other old people confronting him, he drops the ball in front of him. In the next shot the ball is further away from him.
Homer's Triple Bypass - S4-E11
Continuity mistake: When Krusty takes off his shirt, the superfluous third nipple and cattle skull birthmark shown in "Kamp Krusty" are not on his chest. (00:14:50)
Like Father, Like Klown - S3-E6
Continuity mistake: When Krusty has a cigarette during the cartoon just before he is reunited with his father, he keeps his cigarette pack in his shirt pocket, 'close to his heart'. When Krusty and his father hug, the cigarette and the packet are gone.
Continuity mistake: When Homer is kicked out of Moe's the window behind Homer suddenly opens so Moe can throw the record out.
Who Shot Mr. Burns? (1) - S6-E25
Continuity mistake: In this episode, Mr Burns and Smithers are on the balcony of Burns' office. Mr Burns says "It will be like taking candy from a baby. Hey, that sounds like a laugh. Let's try it right now." We see Smithers, whose expression doesn't change as the two go back into Burn's office. In 'Who Shot Mr Burns Part 2', Smithers remembers this event, except now he looks quite shocked when Burns mentions about taking the candy.
Milhouse Doesn't Live Here Anymore - S15-E12
Continuity mistake: Right at the end Lisa is holding a doll head and some cards. There is a very brief shot of Bart, and then when it's back on Lisa she doesn't have anything in her hands when they hug. There wasn't time for them to be put down and you cannot see them anywhere either.
Hunka Hunka Burns in Love - S13-E4
Continuity mistake: In one of the shots after Mr Burns has broken the fortune cookie, the remains of it vanish from the table. There is something else on the table, nearer Smithers, but it and the cookie are very different shapes, so it's very difficult to confuse the two.
Springfield Connection - S6-E23
Continuity mistake: When Marge walks into the hair salon, she is carrying a white bag. But in the next shot when she talks to Mrs Krabappel, the bag is gone.
Much Apu About Nothing - S7-E23
Continuity mistake: When Nelson pulls back Uta, he drops a book. In the next shot, the book has gone.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.