Not much about Doohan is known, but it can be inferred that he is an experienced pilot and mechanic. He lives on Earth with his assistant Miles. At the end of Session 19, he rescues Spike using a remodelled version of the NASA space shuttle, Columbia, which is lead out of the hangar by a tank.
- Doohan's name is a reference to actor James Doohan, who played Star Trek character Montgomery "Scotty" Scott, the chief engineer of the U.S.S. Enterprise.
- Aircraft in Doohan's scrapyard include a B-25 Mitchell, a Mil Mi-24, an F-22 Raptor, and an F-16 Fighting Falcon. The tank which his assistant drives is an M4 Sherman.