Bobby Kills the Fly

“I hit myself on the back of my head with a hammer.”

“That’s too bad. How did it happen?”

“I wanted to kill a fly.”

“Wait a moment, how could you see the fly if it was on the back of your head where the bump is?”

“It wasn’t on the back of my head. It was on the table in front of me.”

“But I don’t understand, then why did you hit yourself on the back of the head with the hammer?”

“Can’t you understand? I wanted to kill it with my forehead.”