From The Guardian mag on Saturday.

Bloke goes to fancy-dress party, but he's in his normal clothes except that he's carrying a young, completely naked woman on his back.

The host says to him, "What have you come as, then?"

Chap says, "I've come as a tortoise!"

Host says, "How do you make that out then? You're in your normal clothes but you just have a naked girl on your back!"

"Yeah," says the bloke. "That's Michelle!"