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.
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.
The New Adventures of Old Tom - S14-E18
Continuity mistake: In the beginning of the episode the sign says "Every B deserves a J" underneath the sign of Jason's Jewelry but when Brian and Stewie go to return it that wording is gone.
Continuity mistake: Peter, Quagmire, Cleveland and Joe are crawling through the air duct. Joes wheelchair is nowhere in sight yet when they fall to the floor it hits Joe in the head. (00:10:18)
The New Adventures of Old Tom - S14-E18
Continuity mistake: Peter goes to the roof where Tom is debating jumping. He has orange fingers because he ate a Doritos taco. He licks two fingers but next shot shows them all clean.