Lois: Brian, you're not wearing the sweater I made you.
Brian: Well, y'know, it's a little warm in here...
Lois: (singing)"Don we now our gay apparel."
(Brian sighs and puts on the sweater)
Brian: It doesn't get much gayer than this.
Another one (about the mistletoe):
Lois: For me? Please?
Peter: All right, all right, but you owe me. Later, under the mistletoe, open
mouth, no matter how drunk I am.
And finally, the very best, when Peter and Brian are planning to steal
Christmas presents from a trailer park home:
Brian: You're really going to take back donated gifts on Christmas Eve?
Peter: Yup, now here's the plan ...
(Peter takes blueprints out of his coat)
Peter: You'll enter through the air conditioning duct here, now there'll be an
invisible laser grid 3 inches above the floor so you'll have to compress your
body to the size of an ordinary household sponge and slide underneath like
some kind of weird amphibious dolphin
Brian: Can I buy some pot from you?
From the "A Very Special Family Guy Freakin' Christmas" episode.