There are twelve astronauts who walked on the moon between 1969 and 1972. Three (Jim Irwin, Alan Shepard, and Pete Conrad) died several years before this documentary was produced. Of the nine surviving moon-walkers, eight were interviewed: Buzz Aldrin (Apollo 11 Lunar Module Pilot), Alan Bean (Apollo 12 LMP), Edgar Mitchell (Apollo 14 LMP), David Scott (Apollo 15 Commander), John Young (Apollo 16 Commander), Charlie Duke (Apollo 16 LMP), Eugene Cernan (Apollo 17 Commander), and Harrison "Jack" Schmitt (Apollo 17 LMP).
Additionally, Michael Collins, who orbited the moon as Command Module Pilot of Apollo 11, and Jim Lovell, who orbited the moon as CMP of Apollo 8 and later looped around it as Commander of the aborted Apollo 13, were interviewed.
The only moon-walker who declined to be interviewed was Neil Armstrong (Apollo 11 Commander and first to walk on the moon), through the filmmakers did correspond with him about it. In the commentary track, the filmmakers state his reason for declining was that to focus on his own personal experiences would be to lose sight of what was ultimately meant to be a collective human experience. Armstrong can be seen in archive footage throughout the film, however, including a brief clip from a press conference the day before the launch. The filmmakers gave him the same caption noting his name and mission as they did the other astronauts.