Continuity mistake: In the principal's office, when everyone's talking about how Chris sent an inappropriate picture, Joe is there. After Joe says "This makes Chris a sex offender", he's got a relatively pointed nose. In the wide shot his nose is rounded.
Continuity mistake: At the start, the rug is next to Lois' feet. When Chris says about Meg's birthday, the rug isn't visible when it should be. (00:00:20)
Continuity mistake: When Lois finds Peter in the fridge, the papers on the fridge simply vanish between shots. (00:06:20)
Barely Legal - S5-E8
Continuity mistake: At the end, Quagmire takes his robe off and is on the floor. When he comes back with the book for Meg, the robe is gone from the floor. (00:20:30)
Barely Legal - S5-E8
Continuity mistake: Meg gets undressed and leaves her dress by the legs of Brian's chair. When the police enter, the dress is gone. (00:18:50)
Barely Legal - S5-E8
Continuity mistake: When Meg leaves the kitchen and Brian puts his coffee mug on the table, its position is constantly changing when talking to Stewie. (00:08:35)
Continuity mistake: When Lois bends down to pick up the CD off the floor in Chris' room, the items around the shirt on the floor change between shots. (00:16:20)
Continuity mistake: When Stewie is talking to the army recruiter, there is 2 stacks of paper on the desk. When he signs up, one of the stacks has disappeared. (00:07:10)
Continuity mistake: At the start, Chris is sat next to Peter at the table with a visible gap between him and Meg. When Lois stands up, Chris is not closer to Meg as the gap has disappeared. (00:02:20)
Continuity mistake: When Chris is saying about the Army being awesome, there is nothing green on his plate. When the shot changes, something green has appeared on his plate. (00:01:20)
Continuity mistake: When Meg gets promoted, there is a gap in the books on the shelf. When she stands up, the gap is gone. (00:18:30)
Continuity mistake: At the start we see Chris place some shorts on top of an orange shirt, with a small amount of orange sticking out the side. When the shot changes, a lot more orange is now showing. (00:00:50)
Continuity mistake: When Peter is going for ice cream, his fork simply disappears from his plate. (00:18:40)
Continuity mistake: When Stewie keeps saying "mum", he's not stood next to a rug. When the shot changes, a blue rug has appeared next to Stewie. (00:11:40)
Continuity mistake: When Peter says about suing Dr. Hartman, Lois is holding Stewie who is asleep and facing Peter. When the shot changes, Stewie is now looking towards Brian. (00:08:20)
Continuity mistake: When Peter is playing with Stewie's nose, Stewie's arms are by his side, but when the shot changes, he's got his arms in front of him. (00:08:10)
Continuity mistake: Lois' breasts grow in size when Peter is trying to get Quagmire to snap out of his trance.
Continuity mistake: Stewie floats over to Chris sleeping on the couch. Next shot shows Stewie getting tangled in the ceiling fan although there wasn't ever one in the living room.
Continuity mistake: When Lois is carrying Stewie down the stairs, the brick patterns in the wall change between the wide shot and the close-ups. (00:14:10)
Plot hole: They're in the Clam complaining that they can't drink when they make the revelation that Brian can because he's technically 56. But Quagmire should be able to drink, as in a much earlier episode, he's revealed to be over 60.
Suggested correction: Quagmire considers the rest of them to be his best friends. He isn't drinking because they can't drink. He is complaining because since his friends can't drink - he won't drink, so he is still pissed.
It's still a plot hole considering Quagmire's age. I think the writers messed up big time.
You make a good point, but it's awkward to be that one person who is drinking while surrounded by people who can't. So, I understand the correction that was submitted above. Because his friends are not drinking, he now feels that he can't.