Kurt is one of Penny's former boyfriends, with whom she lived with for four years after coming to California from Nebraska. A muscular, but not very educated man, Kurt is arrogant and condescending toward the likes of Leonard and Sheldon. Despite his infrequent appearances, he is initially Leonard's primary rival for Penny's affections and arguably the main antagonist of season 1. Though Penny considers him to be a jerk, it takes her some time to get over him, even though he has cheated on her. Kurt has the tendency to be a bully concentrating on Sheldon and Leonard in each episode he is in.
Shortly after their breakup, Penny asks Leonard and Sheldon to get her television from Kurt's apartment, but Kurt apparently finds them irritating and for that takes away their pants in the pilot episode.
He and Penny ran into each other shortly before their first Halloween apart, and Kurt was able to convince her to invite him to her party, where he shows up in a Tarzan costume. He starts trouble with Leonard again, inadvertently driving an upset and drunk Penny into Leonard's arms, in "The Middle Earth Paradigm".
Kurt was once arrested for urinating on a police car while drunk. When they arrested him, it turned out he had a slew of unpaid tickets as well as an outstanding bench warrant. Penny paid his fines to the tune of $1800 but was never repaid. Months later, Leonard learns about this fact from Penny and tries to convince Kurt to repay her. He rebuffs Leonard, but later does repay Penny, without telling her about Leonard's involvement, in "The Financial Permeability". Kurt and Penny have dinner afterwards, with Penny assuming he has changed.
However, it apparently has not led anywhere, as they are not dating in any following episodes, and Kurt has not been seen since. He is mentioned a couple of times in later episodes.
Green = Appeared, V = Voiced, C = Cameo, F = Flashback,
M = Mentioned,
Dark Grey = Did not appear,