"I feel I should provide a larger context. The reactions from both Penn and Teller are even bigger than you realize, and for a particular reason that was by design on Kostya's part. Very smartly, he chose to perform something of his own creation that harkens back to a popular motif in card magic. One with which any magician with a fair working knowledge of his/her craft would certainly be familiar.
Kostya knew this, and also knew that the bad boys of magic had themselves (recently, and on television, even) performed a card trick founded on this very same motif. It was for all these reasons that Penn was getting upset throughout the routine. He knew that he SHOULD know what was happening and how, and yet he knew that he didn't, and it was utterly maddening. There is actually a moment towards the end of the routine when Penn sees a familiar presentational point and it signals him that the work is done. He knows it's all over but the denoument, and yet doesn't know how (this is when he feints throwing his chair). Brilliant.
At the same time, I can tell you that there is no greater sensation for a magician than being truly taken in like this and utterly fooled and astounded by what you think you know. Teller's reaction is proof of this. He is, really, the magician of the two, and a very knowledgeable expert on magic history. That is to say, he knows his sh*t - a fact that Penn alludes to at one point. Toward the conclusion of the routine you can see Teller bouncing like a giddy little boy at the anticipation of what's about to take place, and that's because he simply hasn't seen anything he would've expected to see, and yet realizes Kostya is about to bring the trick to a successful conclusion.
Like a great heist story, or a movie with a twist ending, Kostya trapped them with their own knowledge and used it as a powerful weapon. And nobody knew this more than Penn & Teller, who saw it coming almost from the moment Kostya began, and with each step felt the rug being pulled from beneath them. Wonderful stuff.
*worth noting: this is absolutely pure sleight of hand. There are no special cards or gimmicks aiding Kostya in his accomplishment. It's pure skill. Congrats again, brother! You elevate our craft to art."