Colonel Shaun Geoffrey Christopher, was the son of U.S. Air Force Captain John Christopher. Colonel Christopher was the commander of the first successful Earth-Saturn probe, a manned mission to Saturn, in the late 20th or early 21st Century. He was a reason why Captain Kirk had to find a way to return his father to Earth. (TOS: "Tomorrow is Yesterday")
- Shaun Geoffrey Christopher was named after writer John D.F. Black's three sons: Shaun, Geoffrey and Christopher.
- The exact date of his mission nor the space agency is unknown, however, the timeframe seems to indicate that NASA might be the likely host. Christopher was born sometime after 1969, the year his father was captured by the USS Enterprise. Some references surmise that his mission took place during the 2020s.