Remember when Bob Newhart made an appearance on The Big Bang Theory? Famous for his work in iconic sitcoms like The Bob Newhart Show and Newhart, the legendary comedian graced the Jim Parson and Kaley Cuoco starring show in 2013. However, before joining the cast of the hit CBS sitcom, Newhart had two specific conditions that needed to be met.

Having already made a name for himself with his comedy, Newhart was no stranger to the small screen when he was invited to be a part of The Big Bang Theory.

In fact, his extensive career included roles in various shows, including a brief stint in George and Leo and guest appearances on shows like Mad TV and ER.

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In 2013, Bob Newhart added another milestone to his career by playing Professor Proton, a fictional character idolized by Sheldon Cooper and Leonard Hofstadter on The Big Bang Theory. Chuck Lorre, the creator of the show wanted to collaborate with Newhart for a while. And hence, when an opportunity arose, Lorre seized it by approaching Newhart. However, before agreeing to join the cast, Newhart had two critical requirements.

Firstly, the comedian insisted that his scenes should be taped in front of a live audience, which is the approach he used while filming iconic shows like Newhart, Lucy, Honeymooners, Mary Tyler Moore, and All in the Family. According to Newhart, this method added an energetic and genuine element that was difficult to recreate with pre-recorded laughter.

"No. 1, my scenes had to be taped live. There's a tendency to pre-tape a lot of stuff and put a laugh track on it and you lose something. With Newhart, Lucy, Honeymooners, Mary Tyler Moore, and All in the Family it was always done in front of live audience.

I always felt that the live audience gives it adrenaline. That's the only way I function."

And that was not it. Newhart laid one other condition. And undoubtedly, Lorre could not be more than happy with this one.

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Secondly, Newhart made it clear that he wanted to be a recurring character, a demand Lorre readily accepted. And this helped the creator seal the deal. Interestingly, despite his illustrious career, Newhart was concerned about not being recognized by The Big Bang Theory audience.

The comedian attributed his fear to the age difference and the passage of time. And voicing his worries to Lorre, he suggested that his appearance must be announced before taping. However, fortunately, his fears were unfounded, as the live audience recognized him instantly with applause and immense enthusiasm.

"I asked Chuck, the writers and our director if they were going to announce I'm in the show before the taping. I was a little nervous that the live audience wouldn't recognize me and there would just be silence.

They said, 'We'll come up on you, and thankfully they recognized me; they applauded and stood up."

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The Big Bang Theory saw several cameos throughout its run. With the most prominent appearances being that of Mark Hammill, James Earl Jones, and Carrie Fisher from the Star Wars franchise. However, even though legendary actor Harrison Ford was approached for an appearance, the actor refused to star in the show for some unknown reasons.