Bob Newhart is returning to CBS's "The Big Bang Theory" to guest-star as Professor Proton, Sheldon's fave childhood hero.

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."

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