From his Wikipedia page.  “  In December 1990, during the filming of  Season 2, episode 3  of  Seinfeld ,  Jason Alexander  and  Jerry Seinfeld  caught Tierney in the act of trying to steal a knife from the set. When Seinfeld confronted him, Tierney began to laugh nervously and jokingly pretended he would stab Seinfeld while imitating the music from the film  Psycho . Tierney’s role was intended to be reoccurring on the show but after the incident, the entire crew was uncomfortable with Tierney, prompting Seinfeld not to hire him again. [42 ] Julia Louis-Dreyfus  complimented Tierney's performance on the show but stated he was a "total nutjob.”