As Bob Newhart prepared for his first ever appearance on The Big Bang Theory, he had a very particular worry. He was a dream casting choice for creator of the show, Chuck Lorre, but the executive producer completely ignored Newhart's concern for that maiden appearance.

In the end, Newhart would go on to feature in a total of six Big Bang Theory episodes. His character also carried over into Young Sheldon, the popular spin-off series of the long-lasting CBS sitcom. He appeared in three episodes of that show.

Part of what made TBBT great was the choice of guest stars. Star Trek legend William Shatner is one of the most iconic actors who agreed to make a cameo on the show.

It took some convincing from main cast member Kaley Cuoco, however, for the special appearance to occur.

Jimmy Speckerman is considered by many fans to be the worst ever guest star to feature on Big Bang. Despite this, the producers were so impressed by him that they went on to cast him as Sheldon Cooper's dad in Young Sheldon.

Tech gurus Bill Gates and Elon Musk are other illustrious names who also guest starred on The Big Bang Theory. Gates said he was thrilled at the opportunity to appear on the show, but audience members suggested that the laugh track during Musk's cameo was fake.

It was a different story in Bob Newhart's case, Chuck Lorre's snub towards his concerns notwithstanding.

Bob Newhart Shines As A Guest Star On The Big Bang Theory

When Bob Newhart was first added to the cast of The Big Bang Theory, neither he nor the producers were sure how long he would last on the show. The fact that he ended up appearing in a total of nine episodes of the series and its spinoff was testament to how much he shone, even in a guest starring capacity.

On Big Bang, Newhart played the character of Professor Proton. The show's creators invited him to be part of the series because they wanted someone iconic to portray the role.

Professor Proton was a fictional character who was a famous TV science educator.

The character was a childhood hero to the main characters, Sheldon (Jim Parsons) and Leonard (Johnny Galecki). They grew up watching his science show and were big fans of him. When they discovered that he did private appearances, they hired him to come to their apartment and give them a science demonstration.

Throughout the show, Professor Proton was depicted as having a dry and witty sense of humor, a trademark of Bob Newhart's own comedic style.

Bob Newhart Was Concerned That Fans Of The Big Bang Theory Would Not Recognize Him

Bob Newhart was 83 when he first featured on The Big Bang Theory, and had been active in Hollywood and comedy circles for more than five decades. The actor and comedian was born on September 5, 1929, in Oak Park, Illinois.

His career took off in the early 1960s, when he released a comedy album called The Button-Down Mind of Bob Newhart, which became a huge success and earned him a Grammy Award. The album featured his unique style of comedic monologues, where he played different characters engaged in funny conversations.

In 1961, Newhart began to star in his own sitcom, The Bob Newhart Show, which ran for six seasons on CBS. The show returned in the 1970s, although the actor was now playing a completely different character.

Despite his multiple career accomplishments over the years, Newhart was concerned that fans would fail to recognize him during his maiden appearance on The Big Bang Theory. This was a fact that he would come to reveal shortly after that first cameo.

Chuck Lorre Did Not Share A Similar Fear Over Bob Newhart's First Appearance On The Big Bang Theory

Bob Newhart confessed his fear of not being recognized in an interview with The Hollywood Reporter in May 2013. The last time he had featured on a TV show for more than three episodes prior to that was in George and Leo, another CBS sitcom that aired between 1997 and 1998.

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

As it would turn out, this was not a fear that Lorre himself shared.

The producer seemingly banked on Newhart's legacy in the industry, and believed that fans would definitely know who he was. This perception was proven right in the end.

"[The producers] said, 'We'll come up on you," Newhart added. "Thankfully, [the audience] recognized me; they applauded and stood up. That was very nice." Jim Parsons would later reveal that the legendary star was so emotional that he shed some tears during the standing ovation.