Realty Bites - S9-E9
Continuity mistake: When the real estate team learn that Marge has sold the murder house, Marge is wearing a red blazer but in the shot which faces Marge's back the blazer is missing, then in the next shot Marge is wearing the blazer again.
Realty Bites - S9-E9
Continuity mistake: When Marge finds out the Mr Hutz does real estate, the 'For Sale' sign changes from black to red and then back again.
Realty Bites - S9-E9
Continuity mistake: While Homer is driving Snake's car, he passes a place called Heinrich's Monocle Shop three times.
Realty Bites - S9-E9
Continuity mistake: The Front door of the Murder House has two windows which vanish, and also a door knob that switches sides so the door opens the opposite way.
Realty Bites - S9-E9
Continuity mistake: Snake has an earring in his right ear, but in some shots the earring is missing then reappears, or it switches to his left ear. Also, when Homer and Snake are fighting on the hood of the car Homer's right shoe falls off, but when the car speeds toward the Murder House, Homer is wearing both of his shoes while he and Snake are still fighting on the hood.
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