Kelley had worked with "Star Trek" creator Gene Roddenberry on previous television pilots, and he was Roddenberry's first choice to play the doctor aboard the USS "Enterprise". However, for the rejected pilot "" (1964), Roddenberry went with director Robert Butler's choice of John Hoyt to play Dr. Philip Boyce. For the second pilot, "Where No Man Has Gone Before" (1966), Roddenberry accepted director James Goldstone's decision to have Paul Fix play Dr. Mark Piper. Although Roddenberry wanted Kelley to play the character of ship's doctor, he did not put Kelley's name forward to NBC; the network never "rejected" the actor as Roddenberry sometimes suggested.