Barry Kripke is a Caltech plasma physicist and an unlikable colleague of Leonard and Sheldon. He has a case of rhotacism, where he pronounces "r" and "l" as "w". With a knack for ribbing people, he is an on-and-off friend to Sheldon, Leonard, Howard, and Rajesh.
In his first appearance, he pitted his "kiwwa wobot," the Kripke Krippler (or as he called it, the "Kwipke Kwippwuh"), originally designed for the Southern California Robot Fighting League Round Robin Invitational, against the guys' robot (M.O.N.T.E.) in an unofficial robot battle at the Caltech kinetics lab ("The Killer Robot Instability"). On another occasion, Barry ridiculed Leonard's unsuccessful anti-proton decay experiment, while Sheldon attempted to befriend Kripke in order to gain access to an open science grid computer to carry out research on structure formation in the early universe. However, Sheldon's efforts were abandoned when he realized that Kripke had no say in who used the computer. Kripke comes on to Penny the same way Howard does, after disgusting her by cleaning his gum pockets for new food, but deciding the name Penny wasn't hot enough he proceeded to call her 'Woxanne' (Roxanne), much to her annoyance ("The Friendship Algorithm").
He continued to appear in Season 3, where he mocked Sheldon consistently. Kripke humiliated Sheldon for his retraction regarding his monopolar blunder, and stated that, unlike this situation, Einstein's cited mistake concerning the cosmological constant might have been right all along ("The Electric Can Opener Fluctuation"). He injected helium into Sheldon's office while he was doing a radio interview, sharing it via portable radio in the cafeteria. With encouragement from Leonard and Raj, Sheldon retaliated by dumping foam all over Kripke and the plasma lab while the president of the university and the board of directors were in the room, as he was showing them how a NSA grant was being put to use with a micro-controlled plasma experiment ("The Vengeance Formulation").
A year later, he was invited to Sheldon and Leonard's apartment by Sheldon during the former's attempt to establish a new social group, along with Zack Johnson, Stuart Bloom, and (Sheldon hopes) LeVar Burton, after Sheldon becomes angry with his friends for eating at Raj's apartment. Zack impresses Barry and Stuart with his tale of a naked woman in a hot tub, and later the three end up singing karaoke, much to Sheldon's dismay ("The Toast Derivation").
In this season, Barry tells Sheldon, who still has some rivalry with him, as well as Raj, that Professor Rothman urinated in the particle physics lab again and his retirement potluck had to be moved up. When Raj speaks to his phone Siri, Kripke, still in their office, points out that he too has that phone and complains about voice recognition difficulties, unaware of his own rhotacism. On the matter of the phone, he further reveals his perverse nature as Raj is offended by his negativity regarding Siri ("The Beta Test Initiation").
In "The Rothman Disintegration", Barry argues with Sheldon over who will receive Professor Rothman's office, taking the issue to President Siebert, and challenging Sheldon to a basketball match, a game they are equally bad at. He appears again briefly in "The Stag Convergence" as a party guest before Howard's marriage, but he kept on complaining that there were no strippers.
During the events of "The Tenure Turbulence," Kripke impresses the tenure committee with ease, especially compared to Leonard, Sheldon, and Raj.
After Sheldon retracts his paper on the existence of a new super heavy element in "The Discovery Dissipation", Kripke came to his office to mock him, suggesting that he should take on a superhero identity as "The Retractor". When Sheldon responded with a comment about his speech impediment, Kripke seemed hurt, but actually used Sheldon's apology as the setup for another "Retractor" joke. In "The Relationship Diremption", Barry taunts Sheldon after new discoveries make his twenty years of work on String Theory useless.
In "The Champagne Reflection", Barry is seen as a guest of Sheldon's internet broadcast, "Sheldon Cooper presents Fun with Flags". He is playing the game "Flag or Not Flag" and is shown flash cards and has to identify the flags. He calls out "fwag" or "not fwag" and appears to be very good at the game.
Despite being a stereotypical geek, Barry apparently tries to be fairly sporty, as shown in "The Friendship Algorithm". In that episode, it was implied that he enjoys polo, water polo, and rock-climbing. "The Rothman Disintegration" reveals that Kripke and Sheldon are "equally bad" at sports. Unlike his colleague, Kripke is fully aware of his limitations and shortcomings, even admitting that he is "creepy, pathetic and can't get girls". He has been known to make inappropriate comments to women, photograph his own genitals and upload the shots to the Internet ("The Beta Test Initiation"), and enjoys hanging out at a strip club near his apartment, which has a free buffet ("The Rothman Disintegration"). He also seems to enjoy strippers.
- Kripke appears in all seasons except Season 1.
- One of Kripke's research concentrations is the physics of fusion plasmas, illustrated by his work on a grant proposal for a new fusion reactor. He has also referred to himself as a "stwing pwagmatist", or string pragmatist. As he is a plasma physicist, he most likely studies the connection between string theory and the quark-gluon plasma. (Analogous parameters to those of "classical" plasma physics can be used to characterize the QGP in liquid state.)
- He has many interests, including Star Trek, raffles, karaoke, ventriloquism, polo, water polo and rock climbing, but he doesn't like monkeys.
- Sheldon has seniority over him, arriving at the university before Kripke.
- Barry's Siri recognizes him as "Bawwy" as it stated when he asked it to "wecommend a westauwant" (recommend a restaurant)
- Barry is ostensibly named after philosopher and logician Saul Kripke.
- It's also possible that the name "Kripke" is a play on the name of the software protection program "Crypkey." It could also be a play on words for "Crypt Key" a popular item within MMORPG games.
- Another possible origin could be the name of the 'makeout-place' that is mentioned in Terminator 3 'Mike Kripke's Basement'
- Through all his appearances on the series, the main characters won only once against Krypke, in the episode The Rothman Disintegration.
- In the Mexican version of the show, Barry does not have rhotacism in the first three seasons, but he speaks with a German accent in season 4. It is not until the fifth season that his rhotacism appears.
- Also, in the Brazillian version of the show, instead of rhotacism, he pronounces "s" and "c" as "th", and "r" as "g" (e.g., he pronounces the Portuguese word "restaurante" as "gethtaugante")