Radio Bart - S3-E13
Audio problem: When Homer talks to Marge about Bart's present, the same footage was taken from 'Saturdays of Thunder,' because you can see that Homer's mouth doesn't move right. (00:02:40)
Radio Bart - S3-E13
Revealing mistake: At Wall E. Weasel's, when Nelson is throwing balls into the 'Skeeball' machine, the animation is repeated because Bart keeps moving in and out of the camera's view. (00:04:10)
Radio Bart - S3-E13
Continuity mistake: When Marge puts Maggie to bed, her pacifier changes from red to light brown between shots. (00:08:10)
Radio Bart - S3-E13
Continuity mistake: At the start of the scene where Bart talks to Rod and Todd on the radio, their shirt colors switch. (00:08:50)
Radio Bart - S3-E13
Continuity mistake: When Rod and Todd talks to 'God' on the radio, the antenna keeps changing position for the entire scene. (00:08:50 - 00:09:40)
Radio Bart - S3-E13
Continuity mistake: When Bart realises he left a "Property of Bart Simpson" label on the radio we see the camera zoom to the well and down to the radio. However at the top, all the fun fairs, stalls, police tape and people have vanished. (00:14:50)
Radio Bart - S3-E13
Continuity mistake: In the scene where Bart tries to get his radio back from the well, watch the police barriers. When Lou and Eddie get coffee, they walk through one of the barriers, tearing it. Several shots later, this torn piece has vanished, and then the barriers disappear entirely. (00:15:40)
Radio Bart - S3-E13
Continuity mistake: As Bart gets the rope snug around the tree stump so he can get the radio, the well and the police barriers have vanished. (00:15:45)
Radio Bart - S3-E13
Other mistake: When Bart falls down the well because Eddie tripped the rope, why would there be rocks falling down with him? (00:16:00)
Radio Bart - S3-E13
Continuity mistake: The position of the hole Homer is digging changes position in relation to the well. (00:19:40)
Radio Bart - S3-E13
Continuity mistake: When Homer, Marge and Sting are down the hole and Sting is digging, Homer is wearing a vest. But in the next shot when they find Bart and Homer moves Sting out of the way, he is wearing a shirt. (00:20:50)
Radio Bart - S3-E13
Audio problem: Just after Krusty kicks Sideshow Mel into the big birthday cake on his show, he says "Hey kids" but his mouth doesn't move right.
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.
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