Strong Arms of the Ma - S14-E9
Audio problem: When Marge sprays the pepper spray at Ralph, the line she says after does not match her mouth.
Strong Arms of the Ma - S14-E9
Audio problem: When Homer says he'll eat twice as much, Bart says excellent, but that doesn't match his mouth.
Strong Arms of the Ma - S14-E9
Audio problem: When the woman who smashes the piano says "support the arts", her mouth is open, but it doesn't move.
A Star is Born-Again - S14-E13
Audio problem: When Lenny talks about selling Sara's autograph on eBay, his lips don't match what he says.
A Star is Born-Again - S14-E13
Audio problem: When Homer tells Ned "Flanders, I'm always interested in talking about free milk. And if there's cookies involved, so much the better", his mouth is not in sync with his voice.
Mr. Spritz Goes to Washington - S14-E14
Audio problem: At the end of the episode, when the guy who helped the Simpsons pass the bill says, "I just passed a bill in three hours. Quit complaining," his mouth movements don't match the words.
Scuse Me While I Miss the Sky - S14-E16
Audio problem: In Declan Desmond's film of Springfield Elementary shown at the end, Kearney and Dolph start beating Jimbo up. After Kearney says "Sellout," he says "Yuppie" in Dolph's voice. Then Dolph says "Soccer Mom" but in Kearney's voice.
Dude, Where's My Ranch? - S14-E18
Audio problem: When Bart gets the beavers to knock down the tree so that Clara can walk across, she gets onto it and starts walking gently. But when she walks gently, it sounds like she's walking quickly across the trunk.
Dude, Where's My Ranch? - S14-E18
Audio problem: Homer groans and Mr Burns' lawyer points out that the note that he groans in is A flat. On the version that I heard it on (The Simpsons Christmas 2 DVD) he actually groans in the note A.
Dude, Where's My Ranch? - S14-E18
Audio problem: When Homer and Bart go to destroy the beaver dam, Homer says "Oh, boy" without moving his mouth.
Dude, Where's My Ranch? - S14-E18
Audio problem: When Bart attempts to free Homer from the beavers, he says "I'll save you", but his mouth doesn't match what he's saying.
Dude, Where's My Ranch? - S14-E18
Audio problem: At the recording studio, when Homer sings the Frankenstein and Dr. No line, his mouth doesn't match what he is saying.
Audio problem: When Bart's gang is singing their song and Nelson is playing the banjo, he sings "because she's dead" and plays different notes yet his hands don't move along the neck of the guitar.
Audio problem: When Marge says she wants the padding that goes under rugs her lip movements don't match what she's saying. (00:13:25)
Marge vs. Singles, Seniors, Childless Couples and Teens, and Gays - S15-E8
Audio problem: When Marge says "Save our families" at the beginning of her petition, her mouth doesn't move. (00:14:40)
I, (Annoyed Grunt)-bot - S15-E9
Audio problem: After watching 'Robot Rumble', Bart tries to dissuade Homer from building a robot by listing his other "talents". The voice and Bart's mouth movements don't at all match. (00:06:20)
Audio problem: When Homer says "Burn the truth" after burning his pants, his mouth doesn't match what he is saying.
There's Something About Marrying - S16-E10
Audio problem: Homer is strangling Bart and tells Lisa to hold his spot. You can hear Lisa say, "Why you little," and you can hear Bart choking, but neither of their mouths is moving.
Don't Fear The Roofer - S16-E16
Audio problem: When Marge says "You're drooling on my goodwill pile", her mouth doesn't match her voice.
He Loves to Fly and He D'ohs - S19-E1
Audio problem: When Sveltana says 'Love you' to Homer as he leaves the plane, she just smiles, but her lips don't move. (00:04:58)
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