He is good friends with Chris Carter and, as such, has appeared in many of Carter's television shows, including The X-Files and Millennium. O'Quinn portrayed John Locke in the television series Lost, Admiral Erik Pressman in Star Trek: The Next Generation and most recently appeared as the character Arthur Manchester in Falling Skies.
- Lt. Brian Tillman (TXF: "Aubrey")
- Peter Watts (List of Appearances)
- Darius Michaud (TXF: The X-Files: Fight the Future)
- Shadow Man (TXF: Trust No 1)