As the reigning number-one comedy, The Big Bang Theory is well on its way to becoming a classic. Tonight, the CBS sitcom will receive a very special visit from a man who's no stranger to legendary television, Bob Newhart.
Pics: TV and Movie Cast Reunions
The 83-year-old comedian, best known for his roles on Newhart and The Bob Newhart Show, told our Brooke Anderson he had the time of his life portraying Professor Proton (a childhood hero to Leonard and Sheldon), and even felt a sort of kinship with the gang at TBBT.
"When I walked on that set, it was… it was home," said Newhart. "They just treated me so great."
Apparently, the feeling was mutual.
Video: Bob Newhart’s Favorite TV Memories
"I love him so much, I love him so much, I love him so much," gushed star Kaley Cuoco when ET visited the set shortly after Newhart filmed his role on the show.
"Literally, he is an icon to me," added co-star Johnny Galecki, "I was on cloud nine all week."
Watch the video above for a sneak preview of tonight's episode, plus interviews with Newhart and the cast!
Related: Is 'Big Bang Theory' Cast Like Their Characters?
The Big Bang Theory airs Thursdays at 8 p.m. on CBS.