He has appeared in many other TV shows, such as Doctor Who, The X-Files, Warehouse 13, Battlestar Galactica, Chuck, Dollhouse, Star Trek: Voyager, Leverage and Firefly. He is well known throughout the Sci-Fi genre in TV.
He has been married twice and has three children. He is the son of British actor W. Morgan Sheppard.
He became a United States citizen in 2015.
Mark is sometimes credited as Mark A. Sheppard.
- In response to a fan's question, Mark said he was a "Dean-girl".
- Mark's son Max Sheppard made an uncredited appearance as a demon in season 10 episode "Soul Survivor".