This really happened:

Two coworkers of mine, Bob and Vern, had a long-standing habit of teasing each other about getting old. One day Vern was walking around the office with his fly open, until Bob told him.

While he was zipping up, Vern said: "Well, you know what they say: It pays to advertise."

Bob said: "What are you advertising for? Are you having a going-out-of-business sale?"