On some episodes, the closing credits show a still that is actually from the Star Trek blooper reel. It is a close-up of stunt man Bill Blackburn who played an android in Return to Tomorrow (1968), removing his latex make up. In the reel, He is shown taking it off, while an off-screen voice says "You wanted show business, you got it!"
Assignment: Earth (1968)'s Robert Lansing is the only guest star on this series to be billed at the top of the program - just after the episode's title - rather than in the end credits. After the words, "Assignment: Earth", came, "Guest Star Robert Lansing as Mister Seven."
In a few occasions in the latter part of the first season, the credit, in all-uppercase, for "SCRIPT SUPERVISOR", has the first word misspelled "SCPIPT".
Each season of this show has a different arrangement of the theme music over the closing credits, although not every episode uses the arrangement specific to its corresponding season. For example, Whom Gods Destroy (1969), a third-season episode, uses the second-season arrangement of the theme. As did all episodes produced after it.