Homer Alone - S3-E15
Audio problem: When Lisa screams "Mom" on the way to school, she just leaves her mouth open and doesn't close it. It should sound like "Maaaaaa" if she keeps her mouth open. (00:03:20)
Homer Alone - S3-E15
Deliberate mistake: Arnie says that he drops his bagel. When he does he starts to say it, but when we see the helicopter it has just fallen out. If he dropped it at the time he did, then it would be much further down and wouldn't be visible in that shot. (00:05:20)
Homer Alone - S3-E15
Audio problem: When Marge is running errands, Homer gives her his bowling ball with a bottle cap stuck in a hole. She then takes it to Nicks. When he says, "Sorry lady, you've got the wrong Nicks," he shakes his head and makes an "Ohh" shape with his mouth, not saying anything. (00:03:50)
Homer Alone - S3-E15
Continuity mistake: In the scene Marge goes crazy in the car, Homer is let through, and he passes under 'distressed mother' police tape, but in the next shot, the tape has disappeared. (00:06:40)
Homer Alone - S3-E15
Continuity mistake: In the scene where Maggie rips of the top of her bottle, the milk spills everywhere, including on Marge's face. After this Marge goes really crazy and starts screaming. Right before she does this the milk on her face disappears. (00:04:50)
Homer Alone - S3-E15
Continuity mistake: When Homer is singing to Maggie, he is standing by the bed. But in the next shot, Homer disappears and reappears.
Homer Alone - S3-E15
Continuity mistake: When Marge has finished the list of things to do at Rancho Relaxo she has a list on the bed. When we next see Marge a few seconds later, the paper is gone. (00:17:50)
Homer Alone - S3-E15
Continuity mistake: When Barney is kneeling by The Front door step, a pool of water appears next to him instantly. (00:16:40)
Homer Alone - S3-E15
Audio problem: At the start in the kitchen when Homer, Bart and Lisa are all talking over each other, their mouths don't match what they're saying. (00:02:30)
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