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The Best Episodes Of Star Trek: The Original Series

In 1966, an entire new pop culture universe was born, as Star Trek (known nowadays as Star Trek: The Original Series) debuted on NBC and began its three-season run. While the show's initial life was relatively brief, it found new generations of fans in syndication after being canceled, and over the ensuing decades, it spawned nine (and counting) additional series, 13 theatrical movies, and countless books, comics, magazines, toys, and video games.

At the time it first aired, Star Trek: The Original Series (TOS) was an anomaly on American television — an intelligent science fiction series with regular characters that explored scientific concepts and political or social issues. Captain Kirk (William Shatner), Mr. Spock (Leonard Nimoy), Dr. McCoy (DeForest Kelley), and the crew of the Enterprise encountered, as the show's opening narration put it, "new life and new civilizations" every week. When creator Gene Roddenberry's show was at its best, the aliens or situations our heroes came across challenged their own morals or ethics — and by extension, our own — and gave Star Trek a thematic richness that's still relevant today.

But Star Trek: TOS was also an entertaining series full of action, suspense, and humor, complete with a terrific cast. The best episodes of the show combined all that and more, and while everyone may have their own personal favorites, here's our list of some of the greatest episodes the show had to offer.

The Tholian Web is a bright spot in Star Trek's third season

Star Trek's third and final season was marked by intensive creative upheavals behind the scenes — not to mention drastic budget cuts from NBC — that dramatically impacted the production of the series and contributed to the third season easily being the show's worst.

But season 3 did yield up some exceptional segments, such as "The Tholian Web." In this episode, the Enterprise investigates why the entire crew of the sister ship Defiant has seemingly gone mad and killed each other while the vessel itself appears to be literally dissolving. Kirk is trapped aboard the Defiant as it vanishes into an interdimensional tear in space, with the anomaly beginning to affect the minds of the Enterprise crew, as well. Add some very hostile aliens, and it's a packed episode.

This one works because of the truly alien nature of the Tholians (they're not just the usual human actors with some extra hair or prosthetics on their heads), as well as the tension between Spock and McCoy as they deal with the seeming loss of Kirk and saving the ship. The third season had few bright spots, but this was one of them, and it's an outstanding entry overall.

Charlie X has a truly tragic ending

Just the second Star Trek episode ever aired, "Charlie X" is essentially a character study. Charlie Evans (Robert Walker Jr. in one of the show's standout guest shots) is a 17-year-old orphan who's been stranded, alone, on the planet Thasus since his parents' ship crashed there when he was three years old. After he's rescued and transported to the Enterprise, it quickly becomes apparent that Charlie has incredible powers to manipulate matter. It turns out that the inhabitants of Thasus gave him the powers to survive, but his own immaturity makes it impossible for him to return to his own kind. His ultimate fate is both terrible and moving.

Star Trek would return often to the concept of a child or a childlike entity wielding god-like powers (see "The Squire of Gothos" or "And the Children Shall Lead"). But "Charlie X," scripted by story editor Dorothy "D.C." Fontana — who went on to write several of the show's finest episodes — did it first and did it best. The difference is that unlike Trelane from "The Squire of Gothos," who relishes his powers and sees other creatures as playthings, Charlie just wants to live among his own people and find love and friendship like anyone else. The fact that he can't — and must be condemned to a lonely existence — makes for one of the original series' more poignant and bleak endings.

Shore Leave is a weirdly wonderful Star Trek episode

One of Roddenberry's most inspired ideas on Star Trek was bringing in established sci-fi writers to pen scripts for the show, with the legendary Theodore Sturgeon writing two of its very best episodes. "Shore Leave" was the first, in which the crew of the Enterprise comes upon an idyllic, seemingly empty planet and decides to stop there for a little rest and recreation. But they soon discover that the planet seems to generate whatever each person is thinking about at the moment, whether it be amusing, dangerous ... or even fatal.

The 15th episode aired during the first season, Shore Leave benefited from its location shooting (that first year, it took a while to get the crew off the ship due to budget constraints), its wildly surreal premise, and its plentiful character moments. We get to see Dr. McCoy turn on the Southern charm with a comely female crew member, and Kirk gets to be both a lover and a fighter with figures out of his past — although it's tough to determine which he enjoys more. A bracing mix of humor, suspense and sci-fi weirdness, "Shore Leave" flies by like a breezy vacation getaway.

The Corbomite Maneuver is an awe-inspiring sci-fi showdown

The first episode of TOS filmed in regular production and the tenth aired, "The Corbomite Maneuver" follows the Enterprise into a confrontation with an immensely powerful alien vessel commanded by a species previously unknown to humankind. The ensuing duel of wits between Captains Kirk and the antagonistic Balok becomes a test of Kirk's nerves and personality — one that ultimately leads to enlightenment and understanding.

Like many early, shipbound episodes, "The Corbomite Maneuver" (scripted by sci-fi writer Jerry Sohl) relies heavily on the interactions between members of the crew. The most fascinating of these is Kirk's relationship with the hot-headed young navigator, Bailey (guest star Anthony Call), whom Kirk perhaps sees as a less-seasoned version of himself and is tougher on him for it. That aside, the show's unusual alien (played by Clint Howard, younger brother of Ron Howard) and its awe-inspiring sci-fi elements make this one of the series' best illustrations of its mission statement, "to boldly go where no man has gone before."

The Devil in the Dark teaches a lesson in tolerance

A stone-cold classic written by producer Gene L. Coon (probably the most important behind-the-scenes figure in TOS history after Roddenberry), "The Devil in the Dark" takes place at a mining colony where the workers are getting slaughtered relentlessly by a mysterious creature lurking in the planet's miles of labyrinthine tunnels and caves. Kirk and the Enterprise are called in to investigate, but the captain and Mr. Spock soon learn that the rampaging monster is not at all what it appears to be.

While somewhat infamous for its monster costume (stuntman and creature maker Janos Prohaska in what looks like a giant rubber scab), "The Devil in the Dark" not only manages to sell the creature through Prohaska's movements and well-executed sound effects, but it tells a profoundly meaningful story about fear of the unknown, compassion, and the need for tolerance. In other words, it's a model Star Trek episode in many ways. Spock's mind-meld with the alien Horta is one of Leonard Nimoy's best moments, Shatner is restrained and sensitive, and McCoy gets to roll out his signature "I'm a doctor, not a (fill in the blank)" line for the first time.

The Menagerie is an award-winning two-parter

The only two-part episode of The Original Series, "The Menagerie," has an interesting history. When Gene Roddenberry first pitched Star Trek to NBC, the network commissioned a pilot. That pilot was "The Cage," which featured an almost entirely different cast (except for Leonard Nimoy as Spock and Majel Barrett — later to play Nurse Chapel — as the ship's executive officer). The story involved the ship's captain, Christopher Pike (Jeffrey Hunter), being captured by an alien race with immense telepathic powers but little physical mobility, who wanted to mate Pike with a captured woman and create a race of slaves.

NBC passed on "The Cage," but the network was interested enough in Star Trek to request a second pilot with some cast changes (that show was "Where No Man Has Gone Before," which introduced William Shatner as Captain Kirk). Meanwhile, to help resolve a production logjam, Roddenberry wrote a shell story around the unused "The Cage," in which Spock hijacks the Enterprise to return a now-crippled and disfigured Pike back to the aliens, for reasons known only to him. Most of the footage from "The Cage" was used as flashbacks to show what happened to Pike on his first trip to the aliens' home of Talos IV.

The result was a clever, frequently brilliant melding of Star Trek's "present" and early history, all in service of a story about mercy, loyalty, and the power of perception. Roddenberry won a Hugo Award — science fiction's highest honor — for his script, and deservedly so.

Arena is a thrilling Star Trek episode, even with that cheesy Gorn suit

In "Arena," the Enterprise gets into a deadly chase with a spacecraft belonging to the Gorn, a savage, reptilian race who've apparently destroyed a Federation outpost and its occupants with no provocation. But as the two ships enter unexplored space, both are captured by an even more powerful race calling themselves the Metrons. They transport Kirk and the Gorn captain to a planetoid where they must fight out their differences to the death — with the survival of their ships hanging in the balance.

"Arena" was written by Gene L. Coon but was so similar to a short story of the same name by science fiction writer Fredric Brown that the show — to be on the safe side — called Brown and offered him both a fee and story credit on the episode. Whatever its source, "Arena" is a thrilling, action-packed episode from start to finish, with plenty to say about how simple misunderstandings can lead to deadly conflict and unforeseen consequences. Sure, the Gorn costume looks kind of cheesy these days, but the episode was good enough to get past that.

Amok Time is one of Spock's best episodes

"How do Vulcans choose their mates? Haven't you wondered?" a traumatized Spock asks Captain Kirk in the season 2 premiere of TOS. Written by Theodore Sturgeon, "Amok Time" answers that question. With their devotion to logic suppressing all emotions, the Vulcans must nevertheless undergo the "pon farr" every seven years and return home to take a mate. If they don't, the "blood fever" will drive them to madness and even death.

Such is the dilemma facing Kirk, who must decide whether to disobey a direct order from Starfleet to attend a diplomatic event or possibly let his friend and first officer perish due to extreme horniness. That may sound a little flippant, but the stakes are real, and they get even graver when Kirk beams down as best man, only to find out that his role in Spock's wedding isn't exactly what he planned for.

"Amok Time" is a fascinating (to use Spock's favorite word) exploration of Spock and his culture. Plus, it has Kirk and Spock locked in hand-to-hand combat during its final act, and it also features the first use of the Vulcan hand salute and the greeting "live long and prosper." Some of Star Trek's greatest stories focused on the Enterprise's resident science nerd, and the combination of its intriguing storyline and Leonard Nimoy's fantastic performance make this a must-see.

Mirror, Mirror introduced a wickedly fun universe to Star Trek

The concept of a parallel or "mirror" universe is a well-worn sci-fi staple, but Star Trek brought it to network television in 1967 with this classic second 2 yarn. Penned by Jerome Bixby (who wrote several more Trek entries, plus the story that inspired the movie Fantastic Voyage), "Mirror, Mirror" uses an ion storm to beam Kirk, McCoy, Scotty (James Doohan), and Uhura (Nichelle Nichols) into an alternate dimension where there's a Terran Empire instead of a Federation, and the Enterprise is part of a militaristic fleet that ruthlessly conquers and dominates entire planets.

In other words, it's the exact opposite of the ideals they espouse in "our" universe, and while our quartet's main objective is to get home, Kirk at least tries to convince the bearded and dangerous but still logical "mirror" Spock that the Empire is doomed to failure. In addition to its anti-imperial warning, "Mirror, Mirror" gives a lot of the cast the chance to act deliciously evil, and the mirror universe later reared its brutal head again in Star Trek: Deep Space Nine, Star Trek: Enterprise, and most recently, Star Trek: Discovery.

Journey to Babel brings in the family drama

Star Trek story editor and top-shelf writer D.C. Fontana knocked it out of the park with this heart-wrenching, gripping story that introduced Mr. Spock's parents — his Vulcan father, Sarek (Mark Lenard), and his human mother, Amanda (Jane Wyatt).

Sarek is one of many ambassadors being ferried by the Enterprise to a conference deciding the status of the planet Babel. But soon, murder and terror stalk the Enterprise corridors. An unknown vessel shadows the starship, and an attempt is even made to kill Kirk, forcing Spock to take command while his father lies dying from a heart attack ... with Spock being the only one who can provide the blood necessary for Dr. McCoy to save his dad's life.

Despite all the political intrigue, the heart of the episode is the relationship between Spock and his parents. Estranged from Sarek and emotionally cut off from Amanda, Spock's loneliness never feels more acute, and the episode features some of Nimoy's all-time best work as Spock. This is a complex, thrilling entry and another intriguing look into the character and back story of everyone's favorite Vulcan.

Balance of Terror is a tense game of cat and mouse

Before he was Spock's father in season 2's "Journey to Babel," actor Mark Lenard portrayed another important role in season 1 — the commander of a Romulan warship who plays a deadly game of cat and mouse with the Enterprise in "Balance of Terror." The episode marked the first appearance of the belligerent, tyrannical Romulans, and it's a suspense-laden adventure where one wrong move by either commander could mean the destruction of his ship or all-out war.

What adds to the excellence of the episode are the multiple subplots simmering under the main story. The episode opens with Kirk presiding over the marriage of two crew members, a scene echoed at the end with a much more tragic scenario. There's also the bigotry of the angry navigator Stiles (Paul Comi), who suspects Spock is a spy after it's revealed that the Romulans and Vulcans may be distant relatives. And then there's the growing respect and even admiration between Kirk and the Romulan commander, even if they only meet briefly at the show's conclusion.

This is Trek at its spectacular best, and it's worth noting that in addition to playing a Vulcan and a Romulan, Mark Lenard also played a Klingon in Star Trek: The Motion Picture.

If you like suspense, check out The Doomsday Machine

Filled with tension from start to finish and bolstered by a tremendous score from composer Sol Kaplan (one of the few times that a complete score was written for a specific episode), "The Doomsday Machine" works as both a sci-fi retelling of Moby Dick and a warning against the dangers of weapons of mass destruction.

The Enterprise investigates the fate of sister ship Constellation and learns that it was attacked by a giant robot from a distant galaxy that smashes planets to pieces and consumes the debris for fuel. Its only survivor is its captain, Commodore Matt Decker (William Windom), who beams aboard the Enterprise but soon takes command — despite his shocked mental state — as the planet killer reappears and Kirk is stranded aboard the Constellation.

Sci-fi writer Norman Spinrad's script effectively drives up the stakes — the massive machine is headed for the most densely populated part of our galaxy — even as the conflict between Kirk, Spock and the obsessed Decker threatens to send them all down the berserker's throat. The desperate finale is as suspenseful as they come, capping off one of the most intense Star Trek episodes ever made.

The City on the Edge of Forever is Star Trek: The Original Series' finest episode

This award-winning episode, written by legendary sci-fi author Harlan Ellison (with an assist from several show staffers), is still largely and deservedly considered the gold standard of Star Trek episodes. After Dr. McCoy, driven mad by an accidental overdose of medication, jumps through a time portal and somehow changes history, Kirk and Spock travel through the same gateway to find him and repair the damage. They end up in Depression-era New York City, where Kirk falls deeply in love with a saintly woman named Edith Keeler (Joan Collins), only to learn the event that McCoy prevented, changing all of history, is Edith's death.

Ellison's story spans all of time and space and is suffused with a haunting, melancholy quality that few other Trek episodes have ever quite matched. Shatner gives one of his best performances as the Enterprise captain, effectively delivering both Kirk's dawning horror at the decision he must make and his shattering grief at the show's bleak conclusion. This is both top-notch science fiction and a heart-rending meditation on love, loss, and destiny, as well as the theme — later repeated in Star Trek II: The Wrath of Khan — that the "needs of the many outweigh the needs of the few." It's a poignant message given an absorbing, unforgettable presentation in what remains Star Trek's finest hour.