Burns Verkaufen der Kraftwerk - S3-E11
Continuity mistake: Moe opens the special Duff and foam appears down the bottle that disappears instantly. (00:05:10)
Burns Verkaufen der Kraftwerk - S3-E11
Continuity mistake: After the Germans have bought the plant, Homer takes a bite of his doughnut. The bite changes size between shots when Lenny and Karl ask him why he can't be fired. (00:09:10)
Burns Verkaufen der Kraftwerk - S3-E11
Continuity mistake: When the two Germans are looking at Homer in Moe's, the one's hand is on his paperwork. Camera cuts and it's half off the paperwork now. (00:05:20)
Burns Verkaufen der Kraftwerk - S3-E11
Continuity mistake: Homer pours his bottle of beer into his glass creating foam that is raised above the lip of the glass. Camera cuts and the foam has gone. (00:05:20)
Other mistake: When Moe is calling for a 'Hugh Jazz' there is a shot of the bar and Otto can be seen in the upper right corner. However his face is all distorted and out of proportion. (00:14:30)
Continuity mistake: When Moe gets up on stage with Aerosmith you can see the big "Flaming Moe's" sign behind them. However in the close up the sign isn't visible. (00:13:30)
Continuity mistake: When Homer is smelling the BBQ the smoke that's in front of him vanishes instantly. (00:03:30)
Continuity mistake: The paper that Bart draws Skinner on changes from ruled to plain. (00:14:00)
Other mistake: When watching TV at the start Homer's beer can just says D instead off Duff. (00:02:15)
Like Father, Like Klown - S3-E6
Other mistake: When Krusty leaves the Simpsons, The Front door is just an empty space missing all the details. (00:11:20)
Like Father, Like Klown - S3-E6
Continuity mistake: At the end of Krusty's story the candles have burnt themselves out on the table. However in the next shot they are alight again. (00:10:05)
Like Father, Like Klown - S3-E6
Continuity mistake: Towards the end of the meal, Lisa has some meat left on her plate that disappears in some shots completely. (00:06:55)
Like Father, Like Klown - S3-E6
Continuity mistake: When talking about Jewish people, Homer puts mashed potatoes on his plate that sometime disappear and reappear. (00:06:30)
Like Father, Like Klown - S3-E6
Continuity mistake: Lisa says about Krusty being Jewish and Homer's wine glass swaps side on the table. (00:06:20)
Like Father, Like Klown - S3-E6
Continuity mistake: Homer asks if Krusty is going to eat his meatloaf and is reaching across the table as he does so. The camera changes and he is no longer reaching. (00:06:50)
Other mistake: When the family are having dinner and Homer has a beer, the can is grey instead of the usual red. This is rectified a few seconds later. (00:14:00)
Continuity mistake: The zipper of Burns' radiation suit disappears instantly when he's on the phone to the news station. (00:06:20)
Continuity mistake: Milhouse unwraps his present from Bart and the wrapping paper stays under the box. When he's seen a few seconds later however the paper has gone. (00:01:50)
Continuity mistake: When Bart is writing the card for Milhouse, he is writing on the right hand side of the card. This changes to the left hand side in the close up. (00:01:10)
Continuity mistake: Maggie spits a hotel out on to the board which disappears a few seconds later. (00:16:15)
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