Surprised, the man in front turned and snarled, "Just what the hell are you doing?"
"Well," said the guy, "you see, I'm a chiropractor and I could see that you were tense, so I had to massage your back. Sometimes I just can't help practicing my art!"
"That's the stupidest thing I've ever heard!" the guy replied. "I'm a lawyer. Do you see me screwing the guy in front of me?"