[footfootfoot]

I once saw this hilarious comedian/magician and one of his gags was to get a woman from the audience come up on stage and choose a card from the deck and he would correctly identify it. He has her take the card and place it face up on a stool and then sit on top of it. He then takes a pen-light out of his pocket and asks her to tilt her head back and open her mouth, he shines the light in her open mouth and after a moment or two of peering intently he says, "Nope, that's not gonna work." and then continues with the trick.

His whole routine was brilliant and my stomach ached the next day from laughing so hard.