Here's a groaner from Bob Ruehl...
 

I rear-ended another car this morning. I tell you, I knew right then and there that it was going to be a really bad day.

The driver got out of the other car, and wouldn't you know it! He was a dwarf!! He looked up at me and said, "I am Not Happy."

So I said, "Well, then, which one are you?"

And, that's how the fight started.