Chuck Norris owns the greatest poker face of all-time. It helped him win the 1983 world series of poker despite him holding just a joker, a 2 of clubs, a 7 of spades, and a green number 4 from Uno and a monopoly 'get out of jail free' card.
I was signing the receipt for my credit card purchase when the clerk noticed that I had never signed my name on the back of the credit card. She informed me that she could not complete the transaction unless the card was signed. When I asked why, she explained that it was necessary to compare the signature on the credit card with the signature I just signed on the receipt. So I signed the credit card in front of her.
She carefully compared that signature to the one I signed on the receipt. As luck would have it, they matched.