All Bob Newhart's appearances on The Big Bang Theory to air in TBS marathon

Professor Proton forever.

TBS announced Friday that it will pay tribute to the late Bob Newhart, who died July 18, by airing the six episodes of The Big Bang Theory in which the the alter ego of his character, Arthur Jeffries, features prominently.

Jeffries had used the name "Professor Proton" years ago, when he hosted a children's show that inspired the now-grown main characters, Jim Parsons' Sheldon and Johnny Galecki's Leonard, to pursue careers in science.

Newhart made his first appearance on the hit Chuck Lorre sitcom in its sixth season, and he returned five more times. His last guest spot was in October 2018, and the show ended the following year. All six episodes the legendary comedian filmed — "The Proton Resurgence," "The Proton Displacement," "The Proton Transmogrification," "The Opening Night Excitation," "The Proton Regeneration," and "The Planetarium Collision" — will air back-to-back, from 8 p.m. to 11 p.m. on July 21.

Newhart was awarded an Emmy for his work on the first of the episodes, and he was nominated for two of the others.

He reprised his role on the prequel series, Young Sheldon, on which he appeared in the 2017 pilot and, according to IMDb, via voice in 2019 and 2020.

His work on the CBS show was the last of his acting credits, the first of which he earned in the 1960s.

After his death at 94, several of his costars on The Big Bang Theory remembered him fondly.

Mayim Bialik, who played Amy Farrah Fowler, said in a 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. 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!"

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Kaley Cuoco (Penny Hofstadter) was just as complimentary.

"What a dream it was to witness the genius that was Bob Newhart," she wrote in her Instagram Stories. "He was classy, kind, generous and absolutely hilarious. Every take — every time. Icon forever."

On the same site, Kunal Nayyar, the actor behind the comedy's Raj Koothrappali, wrote simply, "Professor Proton. Our dearest Bob Newhart. RIP. Miss you forever."