Science fiction fans may have take notice of Sheppard with his first foray into genre television with The X-Files episode "Fire", on the show’s now classic first season. From there, he appeared in a myriad of series, including guest spots on Sliders, Star Trek: Voyager, The Invisible Man, Charmed, and two episodes on the beloved space Western Firefly.
After appearing on 6 episodes of 24 in 2006, Sheppard took on the role of eccentric but skillful lawyer Romo Lampkin on Ronald D. Moore’s re-imagined Battlestar Galactica. It was in 2009 that he took on the role of breakout character Crowley, leader of the Crossroads Demons and the new Ruler of Hell, on the hit series Supernatural.
In between, Mark Sheppard’s has had recurring roles in some of the most popular shows, including playing Benedict Valda on Warehouse 13, Canton Delaware in Doctor Who, and James Sterling on Leverage.