The obelisk in this episode, constructed at Franklin Lake in the Franklin Canyon Reservoir above Beverly Hills, was erected in the same spot where Opie Taylor throws a rock into the lake during the opening credits of The Andy Griffith Show (1960).
The only episode in Season 3 to be filmed on location and not entirely in the studio.
After living on the planet Kirk's sideburns lose their distinctive pointed ends and become squared off. This was done to emphasize the passage of time and to show Kirk was becoming assimilated to his new life.
Only in this episode do we see the ship firing its gold deflector beam.
The characters on the asteroid-destroying Obelisk are the basis of the alphabet and characters used by the Predators of the Alien-versus-Predator movie franchise.