Gerrold had wanted to appear onscreen in an episode of Star Trek, particularly "The Trouble with Tribbles". The character of Ensign Freeman, who appears in the bar scene with the Klingons, was originally intended by Gerrold to be a walk-on part for himself, however another actor took the role since Gerrold was deemed too thin at the time. He also had an in-joke cameo of sorts in Star Trek The Animated Series: "More Tribbles, More Troubles" where a very thin Ensign is told to seal off the transporter room area by Kirk. Gerrold also provided the voice for alien Em/3/Green in "The Jihad". While Gerrold appeared as a crewman extra with other Trek fandom notables in Star Trek: The Motion Picture, he did not appear in a Trek series until Star Trek: Deep Space Nine, when he played a security guard in "Trials and Tribble-ations", set during the timeframe of his original episode.
