Comedy legend Bob Newhart agreed to join The Big Bang Theory only after setting two clear conditions. First, his scenes had to be filmed in front of a live studio audience — a non-negotiable for the veteran sitcom star, who believed real laughter gave performances their energy. Second, the role couldn’t be a one-off; Newhart wanted a semi-recurring character.
Both requests were granted, and Newhart debuted in Season 6 as Professor Proton (Arthur Jeffries), the TV scientist who inspired Sheldon and Leonard’s love of science. The role quickly became a fan favorite, leading to multiple appearances across the series and later on Young Sheldon.
Newhart’s final appearance on The Big Bang Theory in Season 12 marked the end of an era — and his last on-screen role before his death in 2024 — cementing Professor Proton as one of the show’s most beloved guest characters.
