Continuity mistake: When Stewie pushes Brian down the stairs, in the background at the moment he pushes him that the stairs are visible behind Stewie as well.
The Father, The Son, and The Holy Fonz - S4-E18
Continuity mistake: When Francis arrives, he changes from standing on the threshold to standing inside the house, even though he could not have moved between shots. (00:01:30)
Continuity mistake: The interior of the Griffins' bathroom changes color (from yellow to blue), when Chris first talks to his pimple.
Peterotica - S4-E24
Continuity mistake: When Peter is reading Lois his erotica in bed, the size of his paper changes just after he says "his really cool spaceship".
Continuity mistake: As Brian is saying "OK, you know what, fine, you are a genius", the glass of water disappears. (00:05:55)
The Father, The Son, and The Holy Fonz - S4-E18
Continuity mistake: When Francis is standing on a chair, nailing the crucifix above the door, the bottom of the crucifix overlaps onto the door frame, but when Francis comes down from the chair, the bottom of the crucifix is above the door frame.
Continuity mistake: When Chris is sitting on his bed talking to Doug, the squares on his quilt pattern get smaller. (00:15:05)
Continuity mistake: When Peter is giving the team steriods, the syringe always goes back to the same place.
Continuity mistake: Just after Lois decides to get rid of Chris's pimple, the pimple changes position in relation to Chris's hair. (00:09:30)
Continuity mistake: When Peter and the rest are at the bar and Quagmire is telling Peter that he looked through his garbage, Quagmire's mug tops up between shots.
Continuity mistake: When the fat guys arrive at Peter's group, pay attention to the Asian guy in the first seat third row. After they open snacks he has switched seats with the other guy in the first seat second row. The guy he swapped seats with hair also changes color. (00:12:40)
Brian Goes Back to College - S4-E15
Continuity mistake: Brian stands outside of the gates of Brown University. The girl entering next to him has a backpack with a top flap that changes from brown to yellow and back. (00:08:05)
Petergeist - S4-E26
Continuity mistake: The table with the TV on in Peter and Lois' room is just a small table at the beginning of the episode when Stewie talks to the poltergeist. But as they speak to Stewie in the TV it's on a high up chest of drawers. (00:08:00 - 00:12:00)
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.
Other mistake: During the Ozzy Osbourne scene, there is a person in the audience with no mouth. (00:16:10)
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: Meg is wearing a pink top and blue bottoms in most of this episode, even when sitting at a table watching TV. Then, a few seconds later, when she demands her mum go get her a bag of Skittles, Meg is now in a solid pink dress.
