Bob Newhart first rose to fame in the 60s when his comedy albums sold in huge numbers. His stand-up routines and acting talent made him a household name. Newhart played Dr. Bob Hartley on The Bob Newhart Show in the 70s. He also played innkeeper Dick Loudon in the 80s show Newhart.

After a decades-long career which saw Newhart reaching legend status, he began a guest role on The Big Bang Theory. Newhart played Professor Proton, a fictional children's show character whom Sheldon and Leonard watched growing up. Newhart's role won him an Emmy in 2013.

Newhart himself also attracted a lot of fans. One of them, Bill Nye, made a guest appearance on the show alongside Newhart. Nye spoke about his admiration for Newhart and even shared some details on what it was like to work with him.

Bob Newhart Said His First 'Big Bang Theory' Appearance Was Like 'Going Back In Time'

Newhart spoke to The Hollywood Reporter on the eve of his first appearance on The Big Bang Theory. When asked why he wanted to take the job, Newhart said it was a welcome change of pace.

"I’ve been approached for other projects — some pilots — and that’s too much," Newhart said. "Emotionally, I couldn’t go through another pilot to series, it takes too much out of you and it’s for the younger people today."

Newhart also said that he knew the show's creator, Chuck Lorre, and was familiar with his past work.

"The Big Bang Theory is well written and it has an incredible cast," Newhart said. "It’s intelligent, which is a vanishing commodity. It’s setup joke, setup joke, setup joke. When we were doing The Bob Newhart Show and Newhart, we’d take a minute to set up a joke, but it paid off because the reaction was huge."

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He continued, "But there seems to be a rhythm now in sitcoms — setup joke, setup joke, setup joke. As a result, the audience doesn’t know what the joke is but they know it’s coming because that’s where it always goes. There’s an internal rhythm. That’s one of the reasons I took The Big Bang Theory."

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Newhart also said that the set resembled the stage where he once shot The Bob Newhart Show.

"It was like going back in time," Newhart said. "It was a relief. You never presume anything. At least in comedy, you get that beaten out of you. You may have done 20 great shows in a row and come to one, and it doesn’t work. You never presume anything. After the taping, they had me come out last and the audience all stood up and applauded. That was it until I went in later to tape a different end tag. It was a great experience and took me back in time."

Bill Nye Shared His Admiration For Bob Newhart After Guest Starring With Him On The Show

After Newhart's first appearance on The Big Bang Theory, he was developing a new fan base.

"I was up in Seattle visiting my daughter," he told Today. "She just had a baby girl. We went up to a restaurant and two young girls came up to me and said, ‘Are you Professor Proton?’ I had to think for a while—‘Yes, yes, I am!’"

For Newhart's second appearance on the show, he worked alongside Bill Nye. Nye spoke about his admiration for Newhart and what his experience was like working with the legend himself.

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"I listened to Bob Newhart’s albums as a little kid," Nye said.

"I was absolutely fascinated with his timing. He would be on the phone with Abraham Lincoln, and as a little kid, I’d think, ‘Wait you couldn’t do that, because there was no phone!’ His timing today strikes me as the same. I just love it. I love standing there waiting for him to lay it down at the perfect time. He’s the real deal. And he acts like I’m some peer—just like him. I don’t know what else to do so I just roll with it. ‘Yes, Bob, I’m an actor just like you.’"

Bob Newhart Had A Sweet Tip For Chuck Lorre As 'The Big Bang Theory' Was Wrapping Up

As The Big Bang Theory wrapped up its final season, Newhart spoke to The New York Post about his time on the show.

"They were selling a bunch of computer nerds [to viewers]. It shouldn’t work, but it struck a chord with the audience," he said. "I like the quality of the writing and it’s an incredible cast. It has to be done in front of a live audience; that’s the only way I’ve ever done a TV show."

Newhart appeared as his Professor Proton character six times on the show. As he maintained from the beginning, his decision to do the show came down to the writing.

"Chuck Lorre and I had talked about working together on various projects … but we couldn’t come up with anything," Newhart said. "One day he came to me and said, ‘OK, I’m here for my annual turndown.’ I said, ‘You know what, Chuck? I really like The Big Bang Theory — I like the quality of the writing.’"

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He added, "The first thing I look at is the writing, of course. You can have the greatest cast in the world but if you don’t have a good script, you’re dead."

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While Newhart didn't appear in the series finale, he did attend the show's wrap party.

"There’s a lot of pressure on that final show," he said. "The last time I did [The Big Bang Theory] I knew they were working on the final show. I said to Chuck, ‘You know, I had a lot of luck where my wife from my first show showed up in the finale. You might want to think about that.’"