Leonard McCoy's 5 Best Star Trek: The Original Series Episodes, Ranked

On "Star Trek: The Original Series," Dr. Leonard "Bones" McCoy's (DeForest Kelley) functional role aboard the USS Enterprise is to serve as its chief medical officer. But his "job," as it were, definitely doesn't stop there. He has a crucial dynamic with both Captain Kirk (William Shatner) and Mr. Spock (Leonard Nimoy), constantly needing to remind the former of ethics and serving as the emotionally fiery counterbalance to the strictly logical latter.

In pop culture, McCoy might not always get the same attention as Kirk or Spock, but he is an undeniably iconic character, as was Kelley's performance of him. In fact, Karl Urban honored Kelley despite being free to make Bones his own, making a point to play McCoy almost exactly like Kelley did while most of the other cast members of "Star Trek" (2009) used only subtle traces of their predecessors' performances (if any).

Even with only three seasons of "The Original Series," McCoy got several episodes where he was the central character, something that not every member of the original crew can claim. More crucially, McCoy gets some of the best stories in the entire series outside of Kirk and Spock, and also plays a pivotal role in a few of the best episodes of "TOS" overall, as our ranking confirms.

One of several "Star Trek" episodes so controversial it was banned, Season 3's "The Empath" had depictions of torture — both physical and psychological — that were a bit too intense for the BBC's liking. In fact, it wasn't until 1994, 26 years after its original debut, that the episode finally aired on U.K. television. But "The Empath" has another crucial legacy: it was DeForest Kelley's favorite episode of "TOS." That alone makes it one of the best McCoy episodes by default.

In "The Empath," Kirk, Spock, and McCoy go to retrieve personnel from a research station before the nearby star supernovas. But what should have been a simple pick-up mission turns into a nightmare as they instead get transported below the surface of the planet where the station is located, and are immediately attacked. A mysterious woman, who cannot speak but possesses the ability to absorb others' injuries, is seemingly trapped with them.

Kirk is taken away and tortured by two alien scientists, who explain that the members of the research station had died after enduring that same torture. Kirk survives the first round of torture, and when the aliens come back for more, McCoy sedates both Kirk and Spock to ensure that they take him instead. Despite being close to death, he refuses to let the woman absorb his injuries, fearing it will kill her– even though her willingness to sacrifice herself is what the scientists need to learn. McCoy risks his well-being not only for his friends, but also a complete stranger, which shows just how seriously he takes his role as protector of the physical and mental health of whoever is around him.

One of the questionable things we ignore about "Star Trek" is how easy it is to travel through time. The crew is frequently faced with a problem that only time travel can solve — so they just leap through time, like it's no big deal. But hey, you can only spend so much time fussing about such things during hourlong episodes that need to tell an entire sci-fi story with a beginning, middle, and end.

All nitpicking aside, "The City on the Edge of Forever" is one of the best episodes of "Star Trek: TOS." The 28th episode of "TOS," it represents a show that had clearly found its groove, knew where it was going, and had a firm grasp on all of its main characters. This is proven by how easily its premise could have devolved into silly gimmickry but instead represents sci-fi television at its finest.

When turbulence causes McCoy to accidentally dose himself with a powerful medicine he was using to treat a patient, he becomes mentally unstable and beams himself to a nearby planet. Kirk and Spock search for him, and they all end up going through a portal that transports them to 1930s New York — where a single action by the doctor changes the course of Earth history. While a great episode for all involved, what makes it special for McCoy is the way he is forced to reckon with his mistake and all the trouble it causes, showing a humility that is rarely required of him — but which he never hesitates to display when needed. It is also Kelley's best performance as McCoy, in "TOS" or otherwise.

In Season 2, Episode 18, "The Immunity Syndrome," the crew receives an indecipherable message from a Vulcan starship, with Spock somehow sensing that the entire crew of the ship had been killed. While investigating the Vulcan ship's last known location, the Enterprise finds itself confronting a monstrous organism that can drain the life energy from all living things — including whole solar systems. 

As the situation grows more dire, it is eventually determined that someone is going to need to pilot a manned probe into the belly of the beast, as it were, in what is presumed to be a one-way trip. McCoy is the first to volunteer, despite the fact that it is essentially a doomed mission. Kirk argues he should go instead, not feeling comfortable ordering any of his crew to carry out such a mission.

Spock points out that a captain's place is with his ship, arguing that he should be the one to go due to his scientific expertise. Kirk makes the incredibly difficult decision as to which crewman to send, choosing Spock based not just on his abilities but his physical stamina. But once again, McCoy proves himself completely selfless and unhesitant in his willingness to sacrifice himself for his friends and crewmates. He is also visibly upset when Spock leaves, presumably going to his death — which shows that McCoy's constant badgering and insulting of Spock belies genuine respect and even affection. Luckily, the mission is a success, and he can resume bickering with his Vulcan frenemy. 

The "Star Trek: TOS" timeline needs some explaining, especially since the initial pilot — which featured Leonard Nimoy as Spock but otherwise an entirely different crew and set of actors — was rejected by NBC. Things were retooled a bit, including the production of a second pilot that ultimately sold the show. Both pilots eventually saw the light of day, but the fifth episode filmed in regular production, "The Man Trap," was broadcast as the official premiere episode of "TOS," while also serving as McCoy's debut.

And what a debut it was, for his character in particular. Kirk and McCoy beam aboard planet M-113 to refill the supplies for a research station there. Things quickly go awry and the crew finds themselves in danger from the last surviving member of the planet's alien race, a shapeshifter that lives off salt and discovers how much of the precious nutrient can be extracted from the human body. 

Where the McCoy of it all comes into play is that the shapeshifter — whose existence is initially unbeknownst to the crew — takes the form of Nancy Crater (Jeanne Bal), a former flame of McCoy's. The shapeshifter uses the pair's history to manipulate McCoy, in the process allowing the audience to see a hint of McCoy's kinder, gentler, more romantic past. The episode is also where the dynamic of Kirk, Spock, and McCoy is established, and proves just how essential McCoy is to that dynamic, and that Kirk and Spock alone wouldn't be nearly as effective without him. 

When ranking all three seasons of "Star Trek: TOS," almost nobody is going to argue with putting Season 3 last. It isn't outright bad, but it's definitely the weakest of the three. That being said, it is also the season that takes some of the most interesting creative swings, and does really fascinating things with the characters. Which makes sense, because there is no way anyone involved could have know they'd go on to star in six movies as well as make various other appearances over the next few decades. It felt a little like going big before these characters went away.

Even the title of the eighth episode of Season 3, "For the World Is Hollow and I Have Touched the Sky," smacks of really pushing the bounds of what "TOS" could do. It also stands as arguably the only episode in which McCoy is clearly the main character of the story, in which he is diagnosed with a terminal illness and not much time left. Faced with his looming mortality — and exhibiting a much deeper fear of it than one might have expected given the frequency at which he is willing to sacrifice himself — McCoy falls in love with and marries the high priestess (Kate Woodville) of an alien race called the Fabrini. 

Thinking he only has about a year to live, and faced with either living out that year and going about his Starfleet duties as usual or choosing love, McCoy chooses love. It's not something fans might expect, and just further shows how complex of a character he truly is. He obviously doesn't die, nor does he live happily ever after with the priestess, but it doesn't make what is learned and revealed in the episode any less impactful.