A man went to his mate's fancy dress party with nothing but a naked girl on his back.

"So what the hell are you supposed to be?" the host asked.

"I'm a snail" the man replied.

"What a load of crap!" the host spat. "How can you be a snail when all you've got is that naked girl on your back?"

"That's not a naked girl, mate" the bloke replied, "that's Michelle."