Giles: "I can't believe you served Buffy that beer."
Xander: "I didn't know it was evil!"
Giles: "You knew it was beer."
Xander: "Well, excuse me, Mr. I-spent-the-60s-in-an-electric-Kool-Aid-funky-Satan-groove."
Giles: "It was the early seventies and you should know better."
Ep: Beer Bad