Big Bang Theory and Young Sheldon Stars Pay Tribute to 'Legend' Bob Newhart: 'Effortlessly Professional' (Exclusive) 

Stars of The Big Bang Theory and Young Sheldon stars are paying tribute to Bob Newhart after his death.

The legendary comedian died on Thursday, July 18 at his home in Los Angeles, Calif. following a series of short illnesses, his publicist Jerry Digney confirmed to PEOPLE. He was 94.

His final acting role was playing Professor Proton (whose real name was Arthur Jeffries) on The Big Bang Theory and its prequel spinoff, Young Sheldon, on nine episodes of television between 2013 and 2020.

As Professor Proton, Arthur hosted an educational children's science show that Sheldon (Jim Parsons) and Leonard (Johnny Galecki) watched while they were growing up. Arthur was also Sheldon's childhood hero and the two got to meet in a season 6 episode of the show when he and Leonard hired him for what he thought would be a children's party. Instead, the grown men just wanted to hang out with Arthur since he made them want to become scientists.

He appeared on six total episodes of the sitcom before making special appearances on its spinoff.

Following the news of his death on Thursday, cast members from both shows paid tribute to Newhart.

The Big Bang Theory's Mayim Bialik reflected on Newhart's impact on her life in an exclusive statement to PEOPLE.

"As a child, the Bob Newhart Show provided countless hours of enjoyment for me – it constituted some of my earliest training in the art of sitcom. When I got to work with alongside him on TBBT, it was absolutely a dream come true," she said. "He was effortlessly professional, poised, hilarious and incredibly approachable. Working with Bob was working in the presence of a true comedy legend – the likes of whom we simple don’t see anymore. How he will be missed!"

Iain Armitage, the star of Young Sheldon, also shared a statement with PEOPLE.

“Bob’s Professor Proton was inspiring to Sheldon, and his career as an actor was inspiring to me. He was loved and will be missed," Armitage said.

The 16-year-old also paid tribute to Newhart in his Instagram Stories on Thursday. "Thanks for being such an inspiring Professor Proton and such an incredible human being," he wrote in a slide, over a photo of Newhart as Professor Proton. "Thinking of you and all who loved you today."

He included a string of broken heart emojis in the slide.

TBBT alum Kaley Cuoco, who played Johnny Galecki's love interest Penny, honored Newhart on her Instagram Story.

"What a dream it was to witness the genius that was Bob Newhart. He was classy, kind, generous and absolutely hilarious," she wrote over a photo of herself and the Elf star in a scene together on the series. "Every take - every time. Icon forever."

Kunal Nayyar, who played astrophysicist Rajesh "Raj" Ramayan Koothrappal on TBBT, wrote over a photo in his Instagram Stories on Thursday: "Professor Proton. Our dearest Bob Newhart. RIP. Miss you forever,"

The Big Bang Theory's co-creator Bill Prady also wrote a tribute to the late comedian on X (formerly Twitter).

"Hard to explain how important Bob Newhart was to every comedian and comedy writer who came after him," he wrote in a post that included a photo of him and the Legally Blonde 2: Red White & Blonde star posing together. "Working with him ever so briefly was one of the greatest joys and honors of my life."

Besides Big Bang Theory and Young Sheldon, Newhart had a long list of television and film credits.

With more than six decades in show business, the beloved entertainer was most remembered for his roles in the CBS series The Bob Newhart Show, which ran from 1972 to 1978, and Newhart, which ran from 1982 to 1990.

He was also known for his deadpan humor, standup comedy and roles in Legally Blonde 2, Elf, ER and the TNT movie The Librarian: The Curse of the Judas Chalice.

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Newhart is survived by his four children, sons Robert and Timothy, and daughters Jennifer and Courtney, as well as 10 grandchildren. His wife Ginnie, whom he wed in 1963, died in April 2023.