The Two Mrs. Nahasapeemapetilons - S9-E7
Audio problem: When Homer is running for the food, after racing in the wheelchair with Jasper, he says 'Eat my dust' but his lips don't move for the 'my dust' part.
The Two Mrs. Nahasapeemapetilons - S9-E7
Continuity mistake: When the garden is seen with Bart throwing Hymns into the fire Apu's mother starts to walk to him and she must walk through a curved green structure.In the next shot of Bart,the structure has gone.
The Two Mrs. Nahasapeemapetilons - S9-E7
Continuity mistake: When we see the garden and Bart throwing Hymns into the fire the large tree is fully green. After the shot of Bart,the camera goes up and we see branches with no leaves on them though.
The Two Mrs. Nahasapeemapetilons - S9-E7
Continuity mistake: When Apu walks down the isle the early shots show that Bart and Lisa are not amongst those either side.When Apu walks by,the shot goes to the ground and they have now appeared.
The Two Mrs. Nahasapeemapetilons - S9-E7
Continuity mistake: The amount of liquified chips in the bag at the home changes depending on the shot.
Continuity mistake: When the "Angel" tells everyone to prepare for the end, Carl is seen with yellow skin.
Continuity mistake: While everyone in Springfield is waiting for the apocalypse, Dr. Hibbert's wife Bernice is seen with yellow skin while she's holding on to him.
Continuity mistake: When Dr. Gould says the DNA test was inconclusive, Apu is seen in the background with yellow skin.
Continuity mistake: During the scenes at the site of the mall during the part where they find the Angel, Skinner's hat disappears and reappears.
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.
Miracle on Evergreen Terrace - S9-E10
Continuity mistake: When Bart pulls the melted tree out of the house, a shovel appears out of thin air so he can shovel snow onto it.
All Singing, All Dancing - S9-E11
Continuity mistake: In the scene where Snake first comes in to shoot the Simpsons, after they sing, he starts singing. When turns his head then turns it back, he blinks and his eyes disappear.
Bart Carny - S9-E12
Continuity mistake: When the Simpsons are cleaning their house, the painting above the chair goes from a picture of Maggie to a picture of a boat.
Bart Carny - S9-E12
Continuity mistake: In the end of the episode when the family has reclaimed the house and are cleaning up the living room. As Homer mentions about letting the Cooders stay, Bart tells Marge to get him away from the window. She is standing right next to the couch in the lounge but the very next shot she lowers her hands and pats the couch yet is now in the family room. (Note: There was a few shots that showed there was two couches so the mistake is with Marge suddenly moving not the couch.).
Bart Carny - S9-E12
Continuity mistake: At dinner when the carny dad is doing his cigarette trick, the shot changes to Bart and Lisa and they have piles of food on their plates. About 10 seconds later Marge gathers the plates up and there is nothing on them. Are we to believe that they ate all this food in such a short space of time?
Bart Carny - S9-E12
Continuity mistake: When Bart starts Hitlers' car moving, for a couple of shots the "Iron Cross" disappears from the side of it.
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