A man walked into a bar with a banana on his head. As he served him, the bartender said, "Look, I don't know if you realize this, but you've got a banana on your head."

"That's okay," said the man. "I always wear a banana on my head on Tuesdays."

"But today's Wednesday," said the bartender.

"It's not, is it?" groaned the man. "Oh no! I must look like a complete idiot!"