When In Rome
Willow enters Buffy's apartment exclaiming "Io, Saturnalia!" Trapped in the middle of a group hug, she continues "...y'know, since that's the old Roman winter celebration, except without pretending to free the slaves for a day and the drunken orgies, and you guys have had nog, and not that I didn't miss you, but this isn't a drunken orgy, is it?"
"No," Buffy says. "Our first Christmas after... will just be a nice, normal, non-mystical holiday."
"Without drunken orgies?" Xander says. "That's crazy talk!"
When Giles arrives with the wine, he's happy he doesn't know why everyone finds this hysterically funny.