 Newhart ended his epic career by playing Professor Proton on two CBS sitcoms, Young Sheldon and The Big Bang Theory. If you would have told me when I was a kid that someday I would be doing science next to Professor Proton, I would not have believed you. If someone had told me that people would still call me Professor Proton when I was 83 years old, I never would have quit smoking. In an interview on PBS in 2014, Newhart recalled what he said to a producer who had asked him to talk faster during a scene.