- An elementary particle, found in the nucleus of all atoms, with a positive charge.
- Typically refers to Professor Proton, the host of a kid's science show when Sheldon and Leonard were growing up.
Season 6, Episode 22 - The Proton Resurgence
Aired May 2, 2013
When Sheldon discovers his childhood hero, Professor Proton - a former TV science show host, is available for children's parties, Sheldon and Leonard hire him to perform for them. Meanwhile, Howard and Bernadette take care of Raj's dog.
Season 7, Episode 7 - The Proton Displacement
Aired November 7, 2013
Sheldon feels snubbed when his idol, Professor Proton, seeks Leonard's help for a science paper instead of his. Sheldon gets his revenge by befriending rival science icon Bill Nye. Meanwhile, Howard's presence at girls' night irritates Raj, who feels he can only be himself around the girls.
Season 7, Episode 22 - The Proton Transmogrification
Aired May 1, 2014
Professor Proton delivers Sheldon a lesson in coping with grief when he suffers a loss just as "Star Wars Day" approaches. Meanwhile, a reflective Leonard and Penny get competitive with proposals to change their relationship, and Amy and Bernadette work on a Star Wars-themed gift for the guys' celebration.
Season 11, Episode 6 - The Proton Regeneration
Aired November 2, 2017
When Sheldon learns that Professor Proton's show is being redeveloped, he decides to audition for the role and ends up in competition with Wil Wheaton. Meanwhile, Penny takes care of Halley when Howard and Bernadette are put on bed rest.