I do a few magic tricks. Here is a stab at how he does it. The deck he using has a number of different cards (or maybe all 52) that he can show. If he just has a limited number in the deck he will continue asking the panel until one picks one of the cards that he has in the deck. If he has all 52 he will do the trick like they showed in the clip. I may be totally wrong but that's my guess.Wow, that was awesome. I hate to go all Penn and Teller right now, but if Simon was not secretly in on the trick then I have no explanation for that.