Bob Newhart's Last Role Before He Died Was This Key Young Sheldon Character

Bob Newhart passed away on July 18, 2024, after a series of brief illnesses. The 94-year-old comic left a wealth of memorable comedic moments behind him — including a whole lot from his memorable "The Big Bang Theory" character Arthur Jeffries Ph.D, best known as that fandom-dividing Professor Proton. In fact, Newhart's final role was on the "Big Bang" prequel series — you may have even forgotten Professor Proton was in the "Young Sheldon" pilot. He also provides voiceovers for two more episodes, Season 3's "Teenager Soup and a Little Ball of Fib" and "A Baby Tooth and the Egyptian God of Knowledge."

Professor Proton, of course, is a vital building block in Sheldon Cooper's (Iain Armitage and Jim Parsons) psyche. The Mr. Wizard-like television host encourages Sheldon's interest in science and becomes his lifelong idol. As Sheldon grows up and attains some of the highest honors his field can offer, he never forgets Professor Proton and tries to involve himself in the man's life — for better or for worse.

"The Big Bang Theory" fans first see Arthur Jeffries/Professor Proton in "The Proton Resurgence," the 22nd episode of Season 6 of "The Big Bang Theory." In it, Sheldon Cooper and Leonard Hofstadter (Johnny Galecki) hire him for a personal appearance ... at their apartment. The good professor is more than a little dismayed to discover he'll be lecturing a group of six adults and finds himself venting to Sheldon and Leonard about the disappointments of his life. The threesome bond and Sheldon and Leonard even become involved in Jeffries' feud with Bill Nye.

The character returns twice during Season 7, first upsetting Sheldon by helping Leonard out on a special project ("The Proton Displacement"), then by passing away, leaving him to cope with yet another death in "The Proton Transmogrification". From then on, Jeffries and his Professor Proton alter-ego would occasionally appear to Sheldon in spirit form. Whenever Sheldon pictures him, he's dressed up in Jedi robes and surrounded by a purple hue, just as force ghosts are in the "Star Wars" story. He even dreams him into the Dagobah System, where Jeffries embarks on a quest for a good sandwich. Such hauntings occur in Season 9's "The Opening Night Excitation," Season 11's "The Proton Regeneration," and Season 12's "The Planetarium Collision."  

Bob Newhart's indelible comedic stylings will forever be missed — but thanks to "The Big Bang Theory" and "Young Sheldon," they'll shine forever, just like the stars Professor Proton sometimes lauded on his show.