A common trope of Star Trek: The Original Series was that the crewmembers who wore red uniforms tended to have a relatively short life span—especially if they beamed down to a planet with the main characters. And the fact is, those officers did tend to drop off quickly in episodes, even if the action took place onboard the ship (and John Scalzi wrote a great meta-novel about this, titled—appropriately enough—Redshirts). But there was one officer who frequently appeared on the show in red, and he survived all the way to the third season, making more appearances than either Sulu or Chekov.
Lieutenant Leslie (played with stone face by Eddie Paskey) first appeared on the show in the second pilot episode, “Where No Man Has Gone Before,” and he became a regular fixture on the U.S.S. Enterprise. He was actually in a blue shirt in that episode, but the uniform colors had not been firmly established at that point. After that, he would frequently appear in a red uniform and seemed to be a jack-of-all-trades. He might be on the bridge as a security officer, he might sit at the helm if Sulu was off duty, he might man the engineering station if Scotty was not on the bridge, and a few times, he even took the conn. So he seemed to know his way around the ship and could step in and work where needed, even helping Dr. McCoy in sickbay a couple of times. (You can read the complete rundown of his appearances at Memory Alpha.)
He did appear to die in the second-season episode “Obsession,” but then he was back on the bridge in the next episode. Allegedly, there was a scene in the original script for “Obsession” where Dr. McCoy administered a potion to Leslie that revived him, but that was never filmed. So even though he appeared to suffer the fate of many redshirts that time around, he was saved offscreen and returned to duty.
Lt. Leslie made appearances in 60 episodes across the show’s three seasons—more than George Takei (52 episodes as Sulu), Walter Koenig (36 as Chekov), and Majel Barrett (34 as Nurse Chapel). But he only had a handful of lines throughout his entire run on the series, the most coming in the episode “This Side of Paradise,” when he openly mutinies against Captain Kirk. One of the reasons he was so prevalent, though, was that he was a stand in for William Shatner and also the hand double for James Doohan (who was missing a finger).
Paskey was around for all three seasons of TOS, but he left in the third year due to back problems and bad headaches (his final episode was “Elaan of Troyius”), and he would eventually retire from acting. And even though he was in 60 episodes of the show, his name only appeared in the credits twice, both times when he had lines of dialogue. He would later appear in the episode “Come What May” of the fan-made New Voyages series, playing the father of Lt. Leslie.
