On The X-Files: Originally airing on November 18, 1994, Firewalker sees Mulder and Scully travel to the volcanic Mt. Avalon to investigate the death of a seismologist. Bradley Whitford plays Daniel Trepkos, the team leader on Mt. Avalon seemingly driven mad by a spore released into the air by their work in the volcano. Most Memorable Moment: Determined to dispose of all those exposed to the spores, Trepkos murders engineer Jason Ludwig with a flare gun and burns the body. How Bradley Whitford Made It Big: After impressive but supporting roles in Universal's Billy Madison and on NBC's ER, Whitford made his debut as a main player as Deputy Chief of Staff Josh Lyman on the critically acclaimed NBC political drama The West Wing in 1999. Whitford was nominated for Emmy Awards each year from 2001 - 2003, winning in 2001 for his portrayal of post-traumatic stress following a near-death experience.