Deliberate mistake: In season 4 episode 7, 'Brian the bachelor'. Cleveland is sitting in a chair in a waiting room and is getting really nervous. Peter tries to help him by tying him to a chair and when that doesn't work, he takes off all of their clothes. Peter ties Cleveland's hands to the arms of the chair and then takes Cleveland's clothes off. He couldn't have taken the shirt off while Cleveland's hands were tied to something without untying him or ripping the shirt, which he didn't do.Jack Kaltenbach
Continuity mistake: In the scene where Stewie is eating chocolate cake, he shoves his head in it and covers himself in cake. However when Peter walks in after having liposuction, all the cake has disappeared and Stewie is now completely clean. The bowl of grapes on the table is also gone. (00:11:40)
Continuity mistake: When we first see the English guy in his car, his crates of goods are stacked askew in the back seat. After Peter's crew shoot the car several times and the car is half-wrecked, the boxes are suddenly neatly packed into the seats. Moments later, we see the boxes piled randomly again. This change happens a couple more times before the scene is over.
Audio problem: When Peter introduces the pope to his friends at work, and he is saying "Remember when we got that stripper for Charlie and it turned out to be his son? I think this is gonna top it" or something along those lines), Peter's mouth very obviously does not sync up with the words being said.Gary O'Reilly
Continuity mistake: When Peter is calling for people to fight Lois, he is standing next to a sign that says "Fight the ass kicking housewife" and has metal rings at the top. When it moves to a closer shot, a hyphen has appeared between "ass" and "kicking". Then, after the space where the commercial break would have been, the sign now says "$10.00" and there are no metal rings. Finally, in the next shot, the sign says "Fight the..." and has metal rings on top. (00:06:55)
Plot hole: Stewie gets out of the car seat and goes back to bed, leaving the blanket at the bottom of the seat. When they get to New York, Lois goes to get him out and realises he's gone. But when they started the trip the blanket was covering the entire seat to make it look like Stewie was still in it. So who ever "covered" him up knew he wasn't in the seat before they set off. (00:13:45)amycamille1975
Continuity mistake: After getting the uranium, Stewie places it in the time pad and then puts the pad in his jacket pocket. After being confronted by Hitler who promises to spare them if they sing a musical number, Mort interrupts them, and it's seen that he is now standing on the time pad.
Audio problem: When Peter goes down to the basement, the Pawtucket Patriot guy appears and Peter thinks he's coming on to him. He says, "Listen, I don't swing that way, pal. I got a date with my female wife, I just came down to get some beers." However, his lips very obviously do not sync up with those words.
Continuity mistake: In the flashback when Peter fights Ernie the Giant Chicken, Peter gets knocked off the top of an eighteen wheeler and grabs the second rung at the bottom of the truck's ladder. But when the truck driver sees the pair in his side view mirror, Peter is hanging off the top of the ladder. (00:02:00)Cubs Fan