“How many librarians does it take to change a light bulb?”
“I don't know but I can look it up for you…”
(One of our maintenance guys told me this one today. Of course, I immediately tried to come up with a “How many maintenance guys does it take to look something up in the ready reference collection?” joke to fire back at him. But I couldn't come up with a witty punchline in that instant. I'm sure something will come to me at 3am this morning. Hmm, I wonder if he's listed in the phone book…)