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.
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.
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.
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)
Burns Verkaufen der Kraftwerk - S3-E11
Continuity mistake: When Mr. Burns shows Smithers the picture of him and Elvis, he is standing beside his desk, which is gone for the rest of the scene. (00:10:30)
Burns Verkaufen der Kraftwerk - S3-E11
Continuity mistake: As Mr. Burns and Smithers are talking on the phone, we see a hand holding the receiver, and when they're finished, the next shot shows us a black skinned referee. His skin color was yellow before. Also, the phone is nowhere to be seen. (00:15:55)
Continuity mistake: As Homer watches TV at the beginning, if you look really closely, you can see the remote on the couch colored to be exactly like brown. It then disappears eventually, and then reappears. (00:01:35 - 00:02:30)
Continuity mistake: In the scene where Homer dodges the cannon ball, he is wearing goggles and a helmet. But when Homer jumps down from the platform and hugs Marge, his helmet and goggles have disappeared.
Homer's Barbershop Quartet - S5-E1
Continuity mistake: When Homer is talking to George Harrison, he sees that he has a brownie. Then he rushes over to a pile of brownies and starts scoffing them down. The pile of brownies doesn't get smaller.
Continuity mistake: As Bart is about to enter his house after trying to impress his friends by krumping, you can see he is entering The Front door. However, in the next shot when he gets inside and Marge is waiting you can see that he has entered the family room, which is only accessible through the back door. Entering by The Front door would place him by the stairs, at The Front of the house.
Like Father, Like Klown - S3-E6
Continuity mistake: When we see the overhead shot of Krusty crying at the Simpsons' table (just before he explains his story), we can see that Krusty has no meat on his plate. When we first see the family and Krusty after the story, there's meat on Krusty's plate. This is visible in the 'Homer's tuxedo' mistake picture.
Like Father, Like Klown - S3-E6
Continuity mistake: During dinner, Krusty does not have a shirt pocket until he pulls out his handkerchief. (00:06:45)