Kurt

Kurt is one of Penny's former boyfriends, with whom she lived 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 apperances, he is initialy Leonards primary rival for Penny's affections and arguably the main antagonist of the first season. Though Penny considers him to be a jerk, it took her some time to get over him, even though he had cheated on her.

Overview
Shortly after their breakup, Penny asked Leonard and Sheldon to get her television from Kurt's apartment, but Kurt apparently found them irritating and for that took thier pants ("Pilot").

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 showed up in a Tarzan costume. He started trouble with Leonard again, inadvertently driving an upset and drunk Penny into Leonard's arms. ("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 unsuccessfully tried to convince him to repay her. He rebuffed Leonard, but later did repay Penny in order to get back together with her, leaving out Leonard's role when telling her what happened. ("The Financial Permeability").

However, it apparently did not lead anywhere, as they are not dating in any following episodes, and Kurt has not been seen since. However, he has been mentioned several times. There has been some spectulation that the way Kurt treated Penny is the reason why she now has commitment issues with Leonard.