Life on the Fast Lane (a.k.a. Jacques to Be Wild) - S1-E9
Continuity mistake: When Homer opens the door with his present, look at the door knocker and you can see that is a completely different one to the one seen at the start of this episode.
Life on the Fast Lane (a.k.a. Jacques to Be Wild) - S1-E9
Continuity mistake: When Lisa asks "What did you get?" when holding the tray, you can see next to her there is a cup, but in the next shot the cup has changed into a glass of milk.
Continuity mistake: Milhouse makes a copy of Bart's photo for a brown skinned boy, but the boy's skin turns yellow when his father scolds him. (00:09:40)
Continuity mistake: When Marge kicks Homer out he turns away from the door. When she slams the door he is now stood facing it completely. (00:12:40)
Continuity mistake: When Homer and Bart are at the cabaret show, Mr. Burns and Smithers are there with two women. In almost all of the shots there is a woman sitting between Burns and Smithers, except in the close-up of them when Burns asks "How does he DO it?". Then Smithers is shown as sitting right next to Mr. Burns. (00:21:00)
Continuity mistake: When Bart and his friends are making copies of the photo of Homer, the banner across the copier says "Copies 5 cents," but when they go to deposit the money it says 10 cents.
Continuity mistake: When Bart is standing under the shelter of "Bon Dormir", the pavement on which he is standing is grey. But when he is talking to a policeman, the pavement is now a more darker grey.
Continuity mistake: When Cesar and Ugolin are eating their lunch, Ugolin's dish only has some potatoes in it. A few seconds later, the dish now has two sausages added to it.
Continuity mistake: When we see Lisa eating her dinner, she has a glass of water by her plate. But when we see a full view of the table, the glass has gone.
Continuity mistake: When Adil is speaking to Lisa at dinner at the Simpsons' house, Lisa has a knife and spoon by the side of her dish. In the next shot, both items have disappeared.
Continuity mistake: When Bart is sitting in the bike passenger seat on his way to the Chateau Maison in France, you can see the seat is coloured brown, but when he arrives at the Chateau, the seat is now blue.
Continuity mistake: When Homer is saying goodbye to Bart at the airport, there is a metal fence behind him that changes position between shots.
Continuity mistake: When Principal Skinner is speaking to Marge and Homer, Homer is lying on the settee and you can see there is nothing beside it, but in the next shot his beer can appears from nowhere.
Continuity mistake: When Principal Skinner rings the doorbell of the Simpsons' house, the handle on the door is pink. But when Marge is at the door, the handle is now light blue.
Continuity mistake: When Principal Skinner and his mother are with Bart and his friends after the toilet prank, you can see Bart has Milhouse, Richard and Lewis are beside him. In one shot, Bart is on his own and the other three boys have gone, and in the next shot, they are back again.
Continuity mistake: Bart throws in a microscope in the cupboard of his bedroom when his mother leaves, but in the next shot the microscope is nowhere to be seen.
Continuity mistake: When Marge leaves Bart's room, you can see there is a cap on the mirror on the drawers, but when we see a full view of the room a couple of shots later, the cap has gone.
Continuity mistake: When Bart discovers a pink box by his bed, you can see there is nothing hanging out from the drawer behind him, but in a close-up of Bart in the next shot, a sock suddenly appears.
Continuity mistake: When Homer falls down the stairs, the toy clown lands behind him and a close-up of Homer shows an orange plant pot by the stairs. But when we see a overhead view of Homer lying down, the plant pot is nowhere to be seen.
Continuity mistake: When Marge enters Bart's bedroom, on the wall you can see a picture of a space rocket and on it there is a red cloth. But when we see a close-up of Marge in the next shot, the cloth has gone.
Answer: I'm not sure if this is the one you're thinking of, but an episode of "Ray Bradbury Theatre," called "A Sound of Thunder," dealt with a similar matter: a group of hunters travel back in time to hunt dinosaurs, only to find things have changed when they get back because someone stepped on a butterfly.
Xofer