During his 45 minute monologue, Einstein explained not only the concepts of space, time, and relativity, but also how he "imagined" complex mathematical concepts. After the show, Duffy doffed his wig and answered questions from the audience: for another 45 minutes!
It's obvious that Hudson enjoys acting as much as the audience enjoys watching and interacting with him afterwards. He'll probably come up with a new act next spring, and we'll probably have him back!