When David Krumholtz landed his first professional gig playing Judd Hirsch's teenage son in Conversations With My Father on Broadway, he couldn't have known that 13 years later he would rise to stardom playing Judd Hirsch's progeny yet again on the series NUMB3RS. As an adolescent, he worked mostly in movies portraying a host of nerdy characters. But as he matured, his roles became much more self-assured, which helped turn NUMB3RS into a hit and his first successful series.