being a Skeptic and a fan of Penn Jillette it was extraordinary to see him guest star. Charlie and Penn really had a nice chemistry and it was really interesting to see Charlie's and his girlfriend's differences on the same subject but both with a different rationality.
Though they could have done a better job with the tank by explaining things differently or using less variables. They did a good job no doubt but the trick when being performed was obvious wasn't actually a magic trick, but part of a TV show.
All in all a good episode to watch giving a light amusement of magic tricks and serious character development for Don due to his mental state.