Bill Nye will also guest-star as himself.
The “Big Bang Theory” episode, set to air Nov. 7, features Professor Proton contacting Leonard to ask for help with an experiment. A scorned Sheldon seeks revenge by befriending a rival science TV host, played by Nye.
Newhart appeared on “Big Bang Theory” earlier this year and earned an Emmy for guest actor in a comedy series for his role as Professor Proton. Nye was recently eliminated as a contestant on ABC’s “Dancing With the Stars.”