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.
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)
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.
And Then There Were Fewer - S9-E1
Continuity mistake: When everyone is in the dining room at the dinner table, the order of where everyone sits changes between shots. In all moments where it shows everyone sitting, the order is Priscilla, Derek, Jillian, Mort, Muriel, and Carl. But in one shot, the order is Priscilla, Derek, Jillian, Muriel, Mort, Carl.
Factual error: The family stays briefly in a British apartment, however the plug sockets displayed are US standard, not UK.
Continuity mistake: Lois and Meg take the red car for their vacation at the spa, but while they are gone, Peter is seen driving it a few times. (00:08:00)
From Method to Madness - S3-E18
Continuity mistake: While Stewie and Olivia are performing, Olivia is wearing a light purple dress. After the performance, when Stewie and Olivia are sitting on the piano talking to their teacher, Olivia's dress and hair bow changes from purple to blue in between shots. She is also wearing dark red lipstick instead of none at all.
The Cleveland-Loretta Quagmire - S4-E5
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)
Continuity mistake: Brian's newspaper's name changes from "Daily Informant" to "Daily Tim...". The newspaper also turns upside down between the two shots. (00:11:15)
The Courtship of Stewie's Father - S4-E16
Continuity mistake: After "Herbert the Pervert" leaves the Griffins' house, the size of the couch in relation to Chris changes distinctly between shots.
Continuity mistake: When Peter and the chicken are fighting, everything in the road vanishes instantly.
Continuity mistake: Stewie tries to get his mind control device back from the kitchen. The cupboard door is open when he falls. In the very next shot, Lois turns the light on in the kitchen, and we see the door has closed without anyone touching it. It is open again after that. (00:09:50)
Continuity mistake: When Peter is testifying in court, the microphone on the witness stand disappears in the shots from the judge's point of view. (00:18:43)
Brian Does Hollywood (2) - S3-E2
Continuity mistake: As Peter and Lois take Stewie to the hotel, as we first see Peter, he has on a blue suit. The next scene we see him, he has on a black suit. Then, as they get called in the room, he has his usual on: green pants and a white shirt. (00:06:05)
Continuity mistake: Stewie forces Lois to breastfeed him, and she undoes her shirt. As Brian and Lois argue about who is going to test her milk, Cleveland barges in and is shot. When Lois jumps up, her shirt is buttoned again, with no time for her to do it.
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.
Other mistake: During the Vagina Monologues show, the pair of legs casts a shadow but the microphone stand doesn't. (00:00:45)
I Never Met the Dead Man - S1-E2
Continuity mistake: When Lois and Peter are in bed prior to the Raisin Bran spoof, in one frame Peter is not wearing glasses, the next close-up he is, and in the next frame he is again without glasses. (00:14:50)
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.
Other mistake: When Stewie sneaks into his parents' room and attaches the breastfeeding pump to Lois, he places the cups too high on her chest for them to be on her nipples. You can see this, especially after he removes the cups.