From Method to Madness - S3-E18
Revealing mistake: After the fight between Stewie and Olivia at the concert hall (followed by their breakup), Simon tells Stewie that the act without Olivia is "over" as he turns to walk off the screen. However, before Simon is even partially out of the shot, he completely disappears. (00:18:45)
Revealing mistake: When Brian and Stewie are on the tourbus, the scenery flashing past is just the same few buildings going by over and over. (00:14:25)
Revealing mistake: When Peter runs across the dock after getting out of the boat, a large chunk of his body is missing.
Revealing mistake: When Dr Hartman collapses, he falls off screen but as he disappears the animation is messed up in that he vanishes before the edge of the shot. (00:06:05)
Revealing mistake: When Lois says to become friends with the bullies and earn their trust, she raises her arm. When she does the animation is messed and and he arm merges with the table. (00:10:00)
Death Lives - S3-E6
Revealing mistake: When Peter first meets Lois's dad, when they are talking, when Carter raises his eyebrows, for a split second, you can see his "extra" set of eyebrows.
Revealing mistake: When Peter says "kicking, Lois?", after being kicked into the stereo, his nose very briefly turns white. (00:20:00)
Revealing mistake: When the candy tree eats the kid, the kid appears mid-screen.
Answer: Lacey Chabert was the actress who originally voiced Meg in early episodes. She left of her own accord due to being in school and other acting work; Seth MacFarlane has stated there was no tension with her leaving, but it makes for a handy joke for the show.
Jon Sandys ★