Sleeping with the Enemy - S16-E3
Continuity mistake: When looking around the course at the beginning we see there is a spinning toy, which you find in some parks, yet when Willy comes along, it has disappeared in the distance. (00:00:40)
Sleeping with the Enemy - S16-E3
Continuity mistake: At the start when Homer is wearing the sweater, when Bart comes in with his test, we see it disappears for one shot, and is then back. (00:02:30)
Sleeping with the Enemy - S16-E3
Continuity mistake: When Lisa is talking to Homer at the start, we see that Homer puts his Duff down on the table, yet for the rest of the scene it isn't there. (00:01:15)
Sleeping with the Enemy - S16-E3
Continuity mistake: When Lisa is making the game right at the beginning, we see her put a line at the bottom of her one, yet when the shot changes, it is gone. (00:00:25)
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