I once worked for a guy who loved to play the straight man to other people's jokes. He would frequently deliberately set up a joke to be completed by someone else.

People would come into our department looking for files. (In those days, a file was a folder full of papers.) They'd say, "I think I saw it here last week."

The boss would assume his most pompous attitude and say, "Around here, we don't think—we know!"

To which the expected punch line was, "Yeah, I don't think you know, either."