Leben was considered to be one of the most controversial and outspoken fighters on the show. In the first episode, he got drunk and urinated on future teammate Jason Thacker’s bed, stealing his pillow afterward. After a heated exchange in the house between Leben, Bobby Southworth and Josh Koscheck, UFC president Dana White set up a match between Leben and Koscheck. Leben would end up losing the two round fight by unanimous decision, complaining afterward that all Koscheck did was “hold him down” and asked Dana White if those were the types of fighters he wanted in the UFC.
Later in the show, teammate Nate Quarry was eliminated from the competition due to an ankle injury and was told he could choose a previously eliminated fighter to replace him. He chose Leben to return to the competition, only for him to be defeated by Kenny Florian due to doctor stoppage in the first semi-final match after Florian opened up a cut above Leben’s eye via an elbow strike.
Despite his losses on the show, neither counted against his professional record. This is due to a law in Nevada (where the show was filmed) that all official fight results must be disclosed immediately after they take place. The show’s producers didn’t want the results spoiled and leaked on the internet, so they decided to just make the matches exhibition bouts.
On April 9, 2005 during the live finale of The Ultimate Fighter, many of the fighters who had been eliminated were invited back to compete in undercard bouts. Thacker didn’t find out about Leben urinating on his bed until he watched the show, and demanded a match against Leben at the finale. The match ended up happening, and Leben won in 1:35 of the first round after referee stoppage due to strikes. Afterward, Leben got on the mic and apologized to Thacker for urinating on his bed, saying he had since given up drinking because of that incident.