ROFL, I just watched the episode last night. He cancels his vacation so Brian can go to Drug Rehab and decides to join up.
One of my favorite Quagmire lines is from that episode.
Brian is sniffing people coming off and Quagmire is like, what do you smell. I smell 2 asian women.
Quagmire: Thats Right
Brian: and a man
Quagmire: You mean 3 women
Brian: sniff, No
Quagmire: How old are you?
Connie: 16
Quagmire: 18?
Connie: Mom...
Quagmire: I like where this is going. Giggady, Giggady, GIG-A-DY.
Definately another classic. Is that the same episode where earlier he walks up to Meg and goes, 18 yet? No and is like Hey Chris how you doing and just walks off.
I don't think it's the same episode, but in that one Chris starts to say something like "Well it's funny you ask..." and Quagmire goes "Yeah that's great" as he walks away.