Major 'The Big Bang Theory' Season 7 spoilers on Bob Newhart's return as Professor Proton

Bob Newhart's two guest appearances on The Big Bang Theory were met with critical acclaim (he won an Emmy) and praise from the show's fans. The character last appeared earlier in Season 7, but he will be back in a few weeks for another episode entitled "The Proton Transmogrification."

Unfortunately, this could be the last time any of us see Newhart on the sitcom, as a taping report from the set reveals that his character, Professor Proton aka Arthur Jeffries, passes away. Leonard (Johnny Galecki) knocks on Sheldon's door and asks to talk to him and informs him of Professor Proton's passing. He hugs Sheldon, which of course confuses Sheldon.

Sheldon insists that he is fine throughout the episode and tells Amy (Mayim Bialik) that he does not want to go to the funeral because everyone cries and blows his or her nose, so he can never tell who is sad and who is sick. Sheldon eventually does get very upset, and Professor Proton appears to him in dream sequences.

Penny (Kaley Cuoco) and Leonard go to the funeral and the two get emotional while there. This eventually leads to them talking about regrets in their life, and Leonard says he regrets not saying yes when Penny proposed to him. He points out that the score is 2-1 in proposals, so Penny proposes again to even the score. Leonard is supposed to just say no, but he says he wants to think about it. Leonard eventually turns her down again, but in the process Penny accidentally asks again so now the score is 3-2.

Check out the full report here and let us know what you think in the comments below.