Continuity mistake: While the Griffin family are at the Heimlich maneuver class, there is a scene where Stewie is talking to a doll and putting his clothes on. You can see that he has no shoes on but when he sticks his feet through the pant leg holes, shoes suddenly come out of the pants and he has his shoes on. (00:04:10)
Factual error: In the very beginning of Perfect Castaway, when Peter is talking to his workers and telling them he's going to have to "put them down", he pulls out a shotgun and four shells. He puts two shells in each barrel, but then continues to shoot 5 times when they jump in the water. First of all the shotgun is a double-barreled, break action type shotgun, so Peter should only have been able to put two shells in it. Second of all, even if he could put two shells in each barrel, he would only be able to fire it four times.
Continuity mistake: In the episode where Brian and Lois get married, Lois confronts Brian after cheating with Peter back at the house. Stewie is playing with a SIMON SAYS game. Look at the SIMON SAYS when he is playing it (up close), after he is done (the close up shot ends), look at the colors again on the SIMON SAYS, they change.
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.
Continuity mistake: When the Griffins are driving to Washington we see a faraway shot of the car driving from left to right. Peter and Lois are in the front and Chris is leaning back on the back seat. In the next shot, Chris is leaning forward against the back of Peter and Lois's seats. (00:19:30)