Character mistake: When all the wives are in the van Lois calls Bonnie "Debbie".
Character mistake: At the end, Brian says, 'I guess some mysteries are better left unsolved' and everyone else murmurs their agreement, yet Bonnie is heard saying, 'Peter's got a point'. She should have said Brian.
Character mistake: After Stewie and Brian go to tell the past versions of themselves not to tell 1999 Brian about 9/11, Stewie then finds out that Brian then told 1999 Brian to write the Harry Potter novels. This would have been impossible because the first Harry Potter novel was published in 1997, 2 years before the time period Stewie and Brian arrive in. (00:16:35)
Character mistake: In "The Drunken Clam", while Quagmire and Joe are playing table tennis, a poster on the wall incorrectly spells "Pawtucket Patriot ale" as "Pawtucket Patrtot ale."
And Then There Were Fewer - S9-E1
Character mistake: When driving to the manor, Lois wakes up and says "Peter, look" as if she knows they are there. She could have not been able to notice this since the trees are blocking all view of the manor. (00:03:00)
Character mistake: Lois says to Quagmire, if you have any questions we'll be right across the street. They live next door obviously, not across the street.
Character mistake: In the cutaway gag involving George and Lorraine McFly from "Back To The Future" Lorraine says she hasn't seen Marty from high school since prom. George, Lorraine and Marty all attended the Enchantment Under the Sea dance in November 1955, not the prom, which is usually held in the spring.
Untitled Griffin Family History - S4-E27
Character mistake: When the family is about to drown in the panic room and start arguing with Peter about not liking "The Godfather," Chris starts listing off the great actors in it. "Robert DeNiro, Al Pacino, I mean, you've never seen...ROBERT DUVALL!" Robert DeNiro is in "The Godfather Part II," but not in the first one. (00:19:30)
A Very Special Family Guy Freakin' Christmas - S3-E16
Character mistake: In the scene with Peter and his buddies downtown, the sign on the store across the street from them on the right side of the screen is misspelled as "Quahog Sporitng Goods."
The Courtship of Stewie's Father - S4-E16
Character mistake: Lois takes a basket of clothes downstairs to wash them. But she puts them in the dryer instead of the washer.
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 ★