Springfield Connection - S6-E23
Revealing mistake: Just after when Marge is reading the book on the sofa she says 'chaos'. On the far left of the screen a large black 'scratch' appears then just slides off.
Tree House of Horror II: A Simpsons Halloween - S3-E7
Continuity mistake: In Dr. Marvin Monroe's office, in the first shot, we can see a garbage can beside his desk. It disappears for the rest of the scene. The desk also moves forward. (00:13:35)
Tree House of Horror II: A Simpsons Halloween - S3-E7
Continuity mistake: As the family looks out the window to see the limo, the light switch on the wall has vanished. (00:03:40)
Continuity mistake: When the newspapers fall on Skinner, the rake in the corner has turned into a shovel. (00:19:10)
Who Shot Mr. Burns? (1) - S6-E25
Continuity mistake: Early on in this episode, Mr Burns says something like "this positivly has to be there overnight", the shot goes closer on every word or so. You can see that the background behind Mr Burns is that of the Plant. But when the shot zooms out, the background is now of one of the corridors.
Revealing mistake: When the riot police are running into the concert, you can see a 'cardboard' police officer leaning against his car, doing absolutly nothing, not even blinking or talking into his police microphone. (00:07:45)
Continuity mistake: At one point Marge says "no guns at the dinner table" and Homer says "you said the breakfast table", then Marge replies "it's the same table". In most episodes they eat dinner at a different table.
Continuity mistake: When Ray Patterson's / Homer's office is shown, the text on the door is different according to the different shots. When the shot is on the door, the writing on the window (Name and Sanitation Commissioner) is close together, but when the shot is from inside the office with the door open, the writing is apart.
Continuity mistake: When Marge comes to pay for her shopping, she empties her left pocket on her coat, but when Sanjay finds it in her pocket, it's in her left pocket. We know it wasn't in her pocket anyway because when Sanjay finds it, it is bigger than the size of her pocket.
Lisa's Pony - S3-E8
Continuity mistake: At one point in the episode, Homer is on the phone with someone in his work station. I forget who it was, but anyway, when you first see him, the wire is coming from the left side of him and when he turns to his right, the wire is coming from the right side of him.
Continuity mistake: When "The Leader's" car drives by, trailing a cloud of dust, the dust doesn't appear on the people's robes until the cloud clears away.
There's Something About Marrying - S16-E10
Continuity mistake: Reverend Lovejoy is unable to cite which book in the Bible condemns homosexuality, but in "Homer the Heretic," he is able to recite, from memory, a completely random Bible verse.
Bart Carny - S9-E12
Continuity mistake: When Principal Skinner is playing the ring toss game, in the end he only has one ring left in his hand. Then, after his mother asks "Why do you always fail?", he throws two more rings trying to win the combat knife.
Continuity mistake: In the opening scene of the episode, envelopes are pushed through a mail-slot on The Front door. However, when Laddie arrives and Bart goes outside to meet him, The Front door's mail slot has disappeared.
Continuity mistake: When all the dads are together in front of Homer's house, one of them is wearing a grey sweater. When they enter the RV the man with the grey sweater doesn't, but throughout the episode he keeps appearing and disappearing on the RV.
Continuity mistake: When Cletus arrives, to get his child back from Selma, we see Lisa wearing purple gloves. In the following shots, as she speaks to Selma, her hands are bare. (00:04:40)
Continuity mistake: The hospital band on Selma's right wrist keeps appearing and disappearing after they watch the menstration video. (00:03:00)
Continuity mistake: After Bart is attacked by the wolf and goes back into class, the banner above the chalkboard that has the alphabet on it is blue. Every time we see the banner after that it is yellow. (00:18:40)
I Love Lisa - S4-E15
Other mistake: When Lisa and Ralph are swinging at the end, they are swinging outside the frame, but the swing is tied at the top of the inside of the frame.
Lisa's Date with Density - S8-E7
Continuity mistake: As Homer is walking out of the Kwik-E-Mart, after Apu refuses him the donut, he has nothing in his hands. In the next shot from outside the store we see him carrying a small paper bag.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.