Revealing mistake: When Brian tells Brooke "I understand", after he thought he was being rejected, his left ear disappears for a single frame.
Continuity mistake: On the tour bus, in one shot we see Meg wearing her outfit that she wore when she had her make-over. Then about 10 seconds later you see her in a different outfit altogether.
You May Now Kiss The...Uh...Guy Who Receives - S4-E25
Continuity mistake: When Peter drives his car in the field it is perfectly visible, but in the next couple of shots the car's gone, and so are the tire tracks.
Petergeist - S4-E26
Other mistake: The Griffins' house disappears when they flee, but when they go to Quagmire's house after, you can see their house when they are at the front door. Quagmire's house is on the right of theirs and the angle of the shot is to the left so it's definitely their house, not Quagmire's other neighbours on his right. (00:16:36)
The Cleveland-Loretta Quagmire - S4-E5
Plot hole: Brian and Peter see Loretta and Quagmire having sex yet, they aren't sure who she's having an affair with. There's no way they couldn't have noticed it was Quagmire - the couch was facing the front door! And obviously Quagmire was on top of Loretta considering the fact that he leans up, says something, then she tells him to get back down here and finish.
Continuity mistake: Lois' breasts grow in size when Peter is trying to get Quagmire to snap out of his trance.
Brian Goes Back to College - S4-E15
Continuity mistake: When Brian arrives at Brown, his bag strap is across his body. When the shot changes, it's just on one shoulder. (00:08:00)
Brian Goes Back to College - S4-E15
Continuity mistake: Louis' hand changes places on the newspaper at the start when talking to Brian. Note its position in relation to the column. (00:02:10)
The Cleveland-Loretta Quagmire - S4-E5
Continuity mistake: When everyone starts playing charades, Joe is acting out a character. He has black shoes on. The boat throws him overboard and when back on the boat his shoes are white.
Continuity mistake: Brian and Stewie see Meg enter Mayor West's motel room. She's wearing a purple dress. They follow them to a restaurant and Meg has her regular hat and outfit on.
Other mistake: Peter says I can't afford to keep you. He puts 4 bullets in the shotgun. He shoots a total of 5 times.
Petergeist - S4-E26
Continuity mistake: Lois slaps the skull out of Peter's hand and it lands on top of the dirt pile. They both turn around to look at the house and the skull is nowhere in sight.
Continuity mistake: At the start of the episode there's no coffee table beside the couch. When Brian is trying to prove to Peter that he has gravitational pull because of his weight, there's now a table with a bowl of fruit and a book.
Petergeist - S4-E26
Continuity mistake: The filing cabinet that was beside the TV moves to the corner beside the desk.
Jungle Love - S4-E13
Other mistake: In the kitchen when Peter is playing with the paddle ball and then Brian confesses to giving Chris the idea about joining the Peace Corp, there is a picture frame on the wall behind Peter. In this is various pictures of the family including Brian. In this, Brian is as a yellow dog despite being white in the series, and even in the scene depicted.
Continuity mistake: At the start in class there are two people behind Meg who both have green tops. When the camera shows the class from the front one of the green tops has changed colour. (00:02:05)
Continuity mistake: Going up the ladder Lois has Stewie in her left arm. However, as she comes through the window he is in her right arm. (00:06:00)
Continuity mistake: When Joe lifts his steak to his mouth you can see a section cut out of the steak on the plate. When he shoots the plate, the steak is whole. (00:01:50)
Brian Goes Back to College - S4-E15
Continuity mistake: When Stewie runs in to film Brian after he got fired, Lois has her arms crossed. When we see it from the camera's POV, her arms are in completely differently positions. (00:07:10)
