'Big Bang Theory's' Bob Newhart Questions Sheldon's Sanity (Exclusive Video)

TV's No. 1 scripted comedy welcomes a comedic icon next week when Bob Newhart guest stars as a boyhood hero of Sheldon's on CBS' The Big Bang Theory.

During the episode, titled "The Proton Resurgence," Sheldon (Jim Parsons) discovers that Professor Proton, the former host of his favorite science show, is still entertaining the masses and hires him to host a private engagement.

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In an exclusive first-look video of Newhart's appearance (above), Sheldon is naturally over the moon when he comes face-to-face with the good-natured professor, but the latter doesn't seem to take his enthusiasm at face value.

"Is he dangerous?!" he asks Leonard (Johnny Galecki), who's equally thrilled to meet an influential personality of his science-loving youth.

Newhart, a six-time Emmy nominee, makes his Big Bang Theory debut Thursday, May 2 at 8 p.m. on CBS.

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"It was incomprehensible; you can't comprehend what it is you're doing," Parsons told The Hollywood Reporter of his experience working with Newhart. "We've had some great people on this set, but he was the first person that I had that feeling of, 'I can't believe you're real.' "

Check out the clip above, exclusive to THR, to see just whom Professor Proton thinks is the real genius. Stay tuned to THR's The Live Feed next week for more on Newhart's Big Bang Theory appearance.

Email: Lesley.Goldberg@thr.com; Twitter: @Snoodit