Zirnkilton made his sole on-screen appearance in the Law & Order original pilot episode, "Everybody's Favorite Bagman," as one of the NYPD technicians conducting covert surveillance of a restaurant where corrupt politicians are dining. He has one line of dialogue: "Look at that. Do you believe these guys?" Zirnkilton has also provided voices for Family Guy and The Rugrats Movie. In addition to those, he also worked for Law & Order creator Dick Wolf narrating Arrest & Trial, a syndicated but short-lived true-crime documentary series which Wolf produced.