A naked man is walking down the street with a woman on his back...

A guy on the other side of the street yells at him, "Hey, what're you doing!?"

The naked man replies, "Don't get all upset. I'm headed to a costume party!"

"As what?" asks the guy.

"As a tortoise! Can't you tell?"

"Well, what's the woman doing on your back?"

"Oh, that's just Michelle."