Continuity mistake: When Bart is trapped in the coffin, the cables leading to the Cadaver Cam TV disappear then reappear. (00:04:10)
Continuity mistake: When the store is being robbed, Homer throws his bag to the side and it lands face down near the stand of chips Homer jumps into. But when they are watching the video of this incident later, the bag is standing upright, far away from the spot it previously was at.
She Used to Be My Girl - S16-E4
Continuity mistake: Lisa puts a statue of liberty head on it's side in her bed to make it look like she's in bed. But when Marge pulls back the covers the head is face up.
Itchy and Scratchy: The Movie - S4-E6
Audio problem: Bart's mouth doesn't move when he laughs after saying "Now's our chance to be bad."

Continuity mistake: When Homer drives his car to work it is lime green instead of the usual purplish color.
Sex, Pies and Idiot Scrapes - S20-E1
Continuity mistake: When Homer has Snake cornered, the second rung on the ladder behind them is broken. In the next shot it's not broken, then it is again.
Homer's Barbershop Quartet - S5-E1
Other mistake: When Bart and Lisa are looking at records, there is a picture of Homer. He had hair at the time the record was made, and the hat he's wearing isn't big enough to cover it, but there's none visible as there should be.

Tree House of Horror XII - S13-E1
Continuity mistake: At the show the school puts on in "Wiz Kids", when the Montymort Dragon is first seen in the cage, the cage has 6 bars at The Front. When Lisa says "Release The Dragon", the cage has 4 bars. When the cage door is being raised, it has 6 bars again. (00:18:45)
Life on the Fast Lane (a.k.a. Jacques to Be Wild) - S1-E9
Continuity mistake: Near the end when Homer is putting the colored ball things in the tube, right before Marge comes up behind him, the stripes on his tie switch sides for one shot.
Revealing mistake: By the end, when fortune teller lays "The Fiance" card on the table, it instantly makes the same angle as other cards lying there, even though the teller's hand is still under it. It doesn't change the angle when she removes her hand from under it, as though it's floating in the mid-air all the time.
Continuity mistake: By the vending machine, Lisa first points her card at the cell on the right, then there's a zoom on the cells and we see her hand starting to point again, but this time at the cell in the middle. In the next shot, she lowers her hand with the card, which however in this shot is pointing at the cell on the right again.
Homer And Ned's Hail Mary Pass - S16-E8
Continuity mistake: Homer is on The Front lawn when the bus of tourists turn up and Mario comes out. Homer gets mad and throws trash cans at Mario, who runs away and climbs up into the tree house which is at the side of the house, but it should be at the back.
Continuity mistake: When Marge is saying she would never have married Homer if she had known it was him in the camp, she is on the couch. But in the next shot, Marge is standing up and the cat and dog are on the couch.
Audio problem: When Homer pulls Lurleen away from her trailer, she says "Ooh" but her lips don't move. (00:09:20)
Marge vs. the Monorail - S4-E12
Continuity mistake: At the beginning of the episode, Homer slides down a big pipe and smashes through one of the windows on the right side of the car. But when Homer crashes into the chestnut tree, it is fully repaired. (00:01:25)
Who Shot Mr. Burns? (1) - S6-E25
Continuity mistake: When Mr. Burns is sitting on Principal Skinner's desk, he takes his cap off and places in on the desk next to him. But in the next shot when Skinner is saying his monopoly is terrible, the cap is gone.
Marge vs. Singles, Seniors, Childless Couples and Teens, and Gays - S15-E8
Continuity mistake: When Bart asks Ms. Krabapple for detention, the piece of paper on his desk disappears. (00:03:05)
Radio Bart - S3-E13
Continuity mistake: As Bart gets the rope snug around the tree stump so he can get the radio, the well and the police barriers have vanished. (00:15:45)