3rd Rock from the Sun - Season 4 Episode 21

Dick is jealous when fellow physics professor Vincent Strudwick publishes a critically acclaimed, bestselling book on physics, and, while Mary busies herself showing the visiting Nobel Prize winners around the campus, he decides to write a second book that will better Strudwick's. He then realizes, however, that he cannot publish all the secrets of the universe without raising unwanted questions, and so looks for another way to get at Strudwick, using Tommy and Alissa - who, it turns out, is Strudwick's daughter. Sally and Don decide to start hanging out as friends, but soon find themselves unable to resist each other.