Tree House of Horror II: A Simpsons Halloween - S3-E7
Audio problem: When Kang and Kodos land in Springfield and hit Mayor Quimby with a club, one of them says something but his mouth is not moving.
Homer's Triple Bypass - S4-E11
Audio problem: When Lisa is watching Homer have the operation, she shouts "below" but her mouth is closed. (00:20:05)
Itchy and Scratchy: The Movie - S4-E6
Audio problem: Bart's mouth doesn't move when he laughs after saying "Now's our chance to be bad."
Audio problem: When Homer pulls Lurleen away from her trailer, she says "Ooh" but her lips don't move. (00:09:20)
Audio problem: When Homer sulks about not knowing anything about Bart, his first words of speech doesn't match his mouth. (00:08:20)
Audio problem: When Bart is reading Marge's police file he says 'Oh, Mum's only been in twice.' But the lip sync is a bit out because it does not match the words he says.
Homer's Barbershop Quartet - S5-E1
Audio problem: In the scene where the Be Sharps first sing "Coney Island Babe" (I don't know what the song's really called) at Moe's, Skinner sings the rhythm. But when they sing the last few lines, you can still hear Skinner's part, but his mouth is moving like the rest of the group.
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.
Audio problem: At the end of the episode the statue of Jimmy Carter with Marge's hairdo is unveiled, and the assembled throng applaud her reaction. They are all chattering away, but no sound is coming out of their mouths - we only hear the sound of clapping.
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 Homer's vigilante group are putting out a leaf fire, Homer says "No burning leaves without a permit" his mouth is not moving.
Audio problem: When Michael and Bart are playing a song to Lisa, Bart uses her bin as a drum. Sometimes you hear tapping, but Bart doesn't touch the bin.
Audio problem: When the old lady is playing the keyboard at Homer and Marge's wedding, her hands don't match the music.
Audio problem: During the party, when Princess Kashmir asks Homer to dance, her mouth doesn't move. (00:08:10)
Audio problem: In the scene where Lisa is presenting her bully repellant at the 'Big Science Thing', when she first walks onstage there are murmurs of disapproval among the scientists, in which you can hear one of them saying, "Let's not listen". But after Lisa sprays the repellant on herself and stops Francine in her tracks, the scientists start murmuring in astonishment. However, if you listen closely, you'll hear the same recording of someone saying, "Let's not listen".
The Old Man and the C Student - S10-E20
Audio problem: At the choir at the start, Lisa's lips don't move when she says "oh no."
Audio problem: When princess Kashmere is introduced, we hear Homer laughing, however we see him eating and not opening his mouth. (00:08:00)
Smoke on the Daughter - S19-E15
Audio problem: When Martin runs with his book when Kirk Van Houten says to Otto "It's for my kid." he shouts "Eureka!" but his mouth says something completely different.
Audio problem: When Laura insults Kerney and Dolph, Dolph speaks but it's Jimbo's voice we hear even though Jimbo isn't there. (00:05:50)
Homer Alone - S3-E15
Audio problem: At the start in the kitchen when Homer, Bart and Lisa are all talking over each other, their mouths don't match what they're saying. (00:02:30)