Marge vs. the Monorail - S4-E12
Audio problem: When goes to the Monorail Café, the woman there says to Marge "Go away" but her mouth doesn't move.
Other mistake: When Lisa checks Marge's resume, she reads it and turns it over. But there is no text on the back as there should be. (00:06:30)
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."
Marge vs. the Monorail - S4-E12
Continuity mistake: At the beginning of the episode, Homer slides down a big pipe and smashes through one of the windows on the right side of the car. But when Homer crashes into the chestnut tree, it is fully repaired. (00:01:25)
Homer's Triple Bypass - S4-E11
Continuity mistake: When Homer begins praying, the room is dark and there is barely any light. When the nurse shushes him, suddenly it's a lot brighter. (00:14:20)
Homer's Triple Bypass - S4-E11
Continuity mistake: When Barney and Moe visit Homer, the vase of flowers disappears and then suddenly reappears at the end of the scene. (00:16:10)
Marge vs. the Monorail - S4-E12
Other mistake: When Homer crashes his car, he just disappears when it hits the tree. (00:01:50)
Marge vs. the Monorail - S4-E12
Continuity mistake: When Grandpa Simpson stands up in The Town hall, the position and amount of paintings on the wall change several times between shots. (00:06:10)
Marge vs. the Monorail - S4-E12
Other mistake: Lanley's desk in his trailer suddenly gets brighter even though none of the lights in the trailer were turned on. (00:12:50)
Marge vs. the Monorail - S4-E12
Revealing mistake: When the passengers board the Monorail, Homer begins pushing two buttons. The second button he pushes is just the counter. There is no button there. (00:15:40)