X-ray glasses

Jon goes to the local novelty shop and finds a pair of x-ray glasses. He checks them out, and isn't fully convinced, but as usual, the store assistant comes along and closes the deal.

On his way home, Jon puts on his new x-ray glasses and, bingo! He sees everyone in the street naked. He takes them off for a moment, and everyone has their clothes on. Puts the glasses back on...everyone is naked! "Cool!"

As he arrives back home, he is eager to show his new toy to his wife, Judi, but can't find her. He goes up to the bedroom and finds his wife and the postman, naked in bed. He takes his glasses off, and the two are still naked. He puts them back on, and they are still naked.

Jon then says: "Damn, I just paid fifty bucks for these and they're already broken!"