Star Trek: The Animated Series is an Animated Adaptation and the first Spin-Off from the original series, continuing the initial five-year mission.

Given the reality that it was produced by Filmation, the animation is typically the studio's ultra-cheap style. However, they more than made up for that with the presence of all of the original cast except Walter Koenig (Chekov), and the writers as well. The result is a show that might not have had the best animation, but still boasts spectacular imagery and believably non-human aliens that the original show could never depict, while still reasonably keeping to its artistic spirit. As a result, this series is the best example of the Animated Adaptation concept in The Dark Age of Animation, and was so good that it won the franchise's first ever Emmy Award.

The Animated Series remains the shortest-lived series of the Star Trek franchise, with just 22 episodes airing over a 13-month period in 1973-74 on NBC. It was also the last Trek series to air in first-run on network television until Star Trek: Voyager debuted in 1995 on UPN. The franchise would not return to the medium of animation again until the release of Star Trek: Lower Decks in 2020.

However, the franchise creator, Gene Roddenberry, later insisted that the animated show be kept out of continuity since he never anticipated that Star Trek would later be revived in live action on such a scale as would happen, with the film series and The Next Generation. Still, many fans insisted that at least the best episode, "Yesteryear", be counted, considering that it gives a valuable look into Spock's youth and character as well as the planet Vulcan, as told by the most authoritative voice on the matter, D.C. Fontana. Because of the information about Vulcan presented in the show, as well as the introduction of the Holodeck and Kirk's middle name, and the fact that many of the Star Trek writers and actors were involved with the production, many fans consider it a part of their personal Star Trek Canon, depicting the final two years of Enterprise's five year mission. In addition, the producers of Star Trek: Enterprise used numerous references from this series. The Star Trek Expanded Universe, already having less of a need to adhere to strict canon, even went so far as to revive the series' Sixth Ranger alien crew members, Cat Girl Lt. M'Ress and tri-symmetrical Lt. Arex.

CBS declared this series full canon around the time they released it on DVD.

The title used here and on the DVD release is a retronym, as the show originally aired as simply Star Trek. It's also known by the more ponderous title of The Animated Adventures of Gene Roddenberry's Star Trek.

In 2018, IDW Publishing used this series for a Crossover with The Transformers, entitled Star Trek vs. Transformers. Read more about tropes pertaining to that particular story on that page.

This series provides examples of:

• AI Is A Crap Shoot: The planetary computer in "Once Upon a Planet", as a result of the Caretaker's death in the time since the Original Series episode "Shore Leave". It creates things like the Queen of Hearts and dangerous animals when nobody is thinking about them, and it captures Uhura.
• Alternate Universe: "The Magicks of Megas-Tu" has a world in which practicing magic is the norm and "The Counter-Clock Incident" has a universe in which everything works backwards, including aging.
• Ancient Astronauts: Kukulkan in "How Sharper than a Serpent's Tooth". He visited Earth in the distant past and was the basis for the Mayan god of the same name, the Toltec god Quetzalcoatl, and the Chinese dragons.
• Animated Adaptation: The best example thereof in the 1970s.
• Animation Bump: A slight example took place in the second season, firstly due to them already having a lot of stock animation from the first season that they were able to re-use, thus letting them give more time and attention to the new animation, and secondly due to first season director Hal Sutherland — whose color-blindness resulted in him often going with muted purple-pink color schemes for episode he directed — being replaced by Bill Reed, who gave the show a somewhat more vibrant visual style.
• Apocalyptic Log: "Beyond the Farthest Star". The dead ship's log entry/warning.
• Artificial Gravity:
  • The Enterprise's computer shuts off the gravity in "The Practical Joker."
  • The fortress in "The Jihad" loses its gravity when the questers try to get at the MacGuffin in its center.
• "Ass" in Ambassador: The title character in "Bem". He swaps out Kirk's and Spock's communicators and phasers for counterfeits, runs off from the landing party, doesn't even bother separating himself to escape when he is first captured, and leaves Kirk and Spock in their wooden cages when he does manage to escape.
• Asteroid Thicket: In "The Pirates of Orion", the Enterprise pursues the Orion ship into one.
• Attack of the 50-Foot Whatever: Apparently, Keniclus' master plan won't work without making Spock enormous, the better to force everyone to be peaceful, apparently. (He himself is also a giant.)
• Barefoot Cartoon Animal: Lt. M'Ress, who wears a full Starfleet uniform, except for footwear. Justified because she has digitigrade paws (meaning she walks on her toes).
• Bathtub Mermaid: In "The Ambergris Element" Kirk and Spock fall victim to a sur-snake while exploring the planet Argo, and are rescued by the natives, who convert them to water-breathers to make recuperating easier. Unfortunately, while this saves their lives and restores their health, Kirk and Spock must reside in a room-sized water tank aboard the Enterprise. This doesn't sit well with Captain Kirk:
  Kirk: I can't command a ship from inside an aquarium.
• Being Watched: Episode "Beyond the Farthest Star". While the Enterprise landing party is on board the alien ship, Dr. McCoy says being on the ship gives him the creeps and that he feels like something's watching them. He's right: there's an intangible alien being on the ship that's trying to return to the Enterprise with the team.
• Big Dumb Object: "Beyond The Farthest Star" featured an alien podship a mile long and 300 million years old whose pods were exploded from the inside. The ship's insectoid crew left behind only a message warning of an invasive being that forced them to self-destruct rather than bringing it to their homeworld, which the mains take down fairly easily. The same ship (or a very similar one) is a level in the Star Trek: 25th Anniversary point-and-click adventure game. Instead of the invader it is occupied only by the trader called Mudd, who has legally established salvage rights. The cause of its destruction is not discovered, but there are plenty of pirates in the area.
• Big Red Button: "Beyond The Farthest Star". The auxiliary warp drive controls are activated with a red button. Kirk presses it to send the Enterprise on a desperate slingshot maneuver to escape the dead star's gravity and get rid of the alien intruder.
• Bowdlerise: By German TV station ZDF.
• Briar Patching: In "The Practical Joker", passing through an energy field causes the Enterprise computer to play jokes on the crew. Captain Kirk pretends to be scared of the field and tricks the deranged computer into taking the ship through the field again, which reverses the effect that made the computer go bonkers.
• Breaking the Fourth Wall: The huge wink Kirk gives the camera following Scotty's Incredibly Lame Pun at the end of "More Tribbles, More Troubles."
  • Sulu does the same at the end of "The Infinite Vulcan."
• Broad Strokes: The timeframe this series depicts is an accepted part of Star Trek lore, but the actual details have been rearranged since.
• Build Like an Egyptian: Kukulkan's city in "How Sharper than a Serpent's Tooth" has the Mayan pyramids.
• Canon Discontinuity: The series was declared non-canon by Gene Roddenberry himself, with the sole exception of the episode "Yesteryear". (Until CBS later declared the whole thing canon, anyway.)
• Canon Immigrant: The Kzinti, never mentioned or referenced again in the series, from Larry Niven, starting with the CBS re-canonization of the series. They have been major features in Star Fleet Battles, since its license included all elements of the original and animated series.
  • Wasn't for lack of trying, though — there were multiple attempts to re-include the Kzinti in some fashion, but for one reason or another these plans never got started; Star Trek Online got stymied by legal reasons and had to substitute the Ferasan for the Kzinti; it wouldn't be until Lower Decks (appropriately enough) that the species made a reappearance.
• Cat Folk: The Caitian Lieutenant M'Ress, as well as the Kzinti in "The Slaver Weapon". Some of the Expanded Universe material around it suggests that the Caitian relationship to the Kzinti is essentially the same as the one between the Vulcans and the Romulans, only with the ones that left (the Caitians) being the "good guys" that ended up part of the Federation and the ones that stayed (the Kzinti) as the militaristic bad guys with historic conflicts with the Federation (and possibly with some ill-advised genetic engineering on the part of the Kzinti).
• Cat Smile: Lieutenant M'Ress has one constantly, due to her cat-like anatomy.
• Character Development: Since this is a Saturday-Morning Cartoon directed at children (albeit a very well-written one), Kirk's infamous womanizer tendencies are effectively absent here. In particular, he repeatedly rebuffs advances from an attractive woman in "The Jihad," saying they need to focus on the mission at hand.
  • Episodes like "The Slaver Weapon," "The Infinite Vulcan," and "The Lorelei Signal" give Sulu and Uhura more to do than they usually got on the Original Series.
• Chekhov's Gun: In "How Sharper than a Serpent's Tooth", Dr. McCoy's medical kit provides a hypo to calm the Capellan Power Cat.
• Children Are Cruel: In "Yesteryear", we get our first glimpse at Spock's childhood... and it's not pretty.
• Cloning Blues: In "The Infinite Vulcan", the giant clone of Spock experiences an existential crisis when he realizes he is quite out of scale with the Enterprise and everything he is familiar with. He ultimately elects to remain on the planet.
• Comic-Book Adaptation: IDW's Star Trek vs. Transformers used the character designs from the Animated Series, to bettter blend in with the animated characters from The Transformers. It was a good choice, and the characters look surprisingly natural standing next to each other.
• Continuity Nod: Sulu is quite interested in the plant life of Phylos, harking back to his garden in one episode of the live-action series.
  • As in "Journey To Babel," the Orions are again depicted as pirates in "The Pirates of Orion," though their name is pronounced "OR-ee-on" throughout the episode for some reason. Also, they're depicted as blue-skinned here rather than green. ^note  In "Journey to Babel," the only male Orion we meet in TOS is disguised as a blue-skinned Andorian. In "The Menagerie" and "Whom Gods Destroy" we only see female Orions. In other appearances since the original series, we see male Orions as well, and they are green.
• Contrived Coincidence: "How Sharper than a Serpent's Tooth". If Ensign Walking Bear hadn't been on the bridge, Kukulkan would have destroyed both the Enterprise and the entire human race.
• Creator In-Joke: Captain Robert T. April in "The Counter-Clock Incident". April was the original name for the character that eventually became Kirk.
• Crossover: One episode was a nearly 1:1 adaptation of a Known Space short story, save for Kirk and the gang as the heroes; specifically "The Soft Weapon," called here "The Slaver Weapon." The belligerent, lynx-like Kzinti find a shape-shifting Swiss-Army Weapon that looks like a watermellon on a pistol grip, and try to use it to start a fifth man/kzin war.
• Darker and Edgier: Than most other cartoons on television at the time. The Animated Series tended to work with the same style of cerebral stories that the previous live-action series did, and references to death were not glossed over at all. In fact, "Yesteryear" deals with a child version of Spock losing his beloved pet, and the "death words" weren't glossed over or replaced with Lighter and Softer equivalents. This has helped the series gain a strong following within the Star Trek fan community, as well as with the creative staffs involved with the franchise.
• Detachable Lower Half: The title character in "Bem" has the ability to separate his body into different parts.
• Detachment Combat: The title character in "Bem" was a colony creature who could separate his head, upper torso, and lower torso (at least).
• Did We Just Have Tea with Cthulhu?: In "Once Upon a Planet", several characters end up roasting marshmallows with the dragon that was trying to kill them a few minutes earlier.
• Did You Just Punch Out Cthulhu?: "The Magicks of Megas-Tu" has James T. Kirk defeating Satan! (Or at least a being claiming to be him as part of a Secret Test of Character.) For an added bonus, they become friends at the end.
• Dolled-Up Installment: "The Slaver Weapon", from Larry Niven's "The Soft Weapon".
• Doomed Defeatist: Subverted with M-3-Green in "The Jihad", who despite calling their mission "mad" and saying "We're all going to die", makes to the end alive.
• Empowered Badass Normal: Kirk (and a few others) gain magical abilities in "The Magicks of Megas-Tu".
• Energy Beings: In "Beyond The Farthest Star", a being made out of magnetic energy tried to take over the Enterprise.
  • In "Bem", one of these was protecting a primitive species from outside interference.
• Energy Ring Attack: One episode has a Klingon warship test out a stasis field ray against the Enterprise. When fired, concentric circles engulf the Enterprise, immobilizing it. The stasis ray is also fired at two supply drones that the Enterprise was escorting.
• Everyone Is a Super: "The Magicks of Megas-Tu" has beings who have the ability to practice magic.
• Expressive Ears: The Kzinti in "The Slaver Weapon" lay their ears back when angry..
• Expospeak Gag: Between Spock and McCoy.
  McCoy: Why couldn't you have just said [x]?
  Spock: I believe I just did.
• Extreme Close-Up: Used frequently, often with the speaking character's mouth out of frame (presumably to save on animation costs)
• Fainting: Kirk does something akin to the exhaustion- or anemia-based variety in "Albatross" when The Plague kicks in. Luckily, Spock is there to catch him. Also, in "Pirates of Orion", the first sign that something is seriously wrong with Spock happens when he collapses suddenly.
• Females Are More Innocent: "The Lorelei Signal". The women of the planet Taurus II are effectively psychic vampires who drain the energy from men to survive, and have been doing so to the crew of passing ships for at least 150 years. They try to do the same to Kirk, Spock, and Dr. McCoy and are only stopped by threat of force from Uhura... yet they're still presented as sympathetic to both the viewer and the heroes because they "cannot bear children," and the end of the episode has the Enterprise crew promise them a ship to be able to leave their planet and thus escape the "curse" of immortality.
• Fish People: "The Ambergris Element" features fish-like aliens who can only breath underwater.
• Five Year Plan: The three seasons of The Original Series and the two seasons of The Animated Series comprise the "five-year mission to explore strange new worlds" from the famous Opening Narration (which is present in full in this series).
• A Form You Are Comfortable With: "The Magicks of Megas-Tu". The inhabitants of Megas-Tu do this for their own bodies and their planet's surface for the benefit of the Enterprise crew.
• For Want of a Nail: In "Yesteryear", if Spock hadn't saved his past self, he wouldn't be alive in order to be part of the Enterprise crew.
• Forgotten Phlebotinum: "Life-support belts" that allow the crew to survive in vacuum without spacesuits only ever appear in this series.
• Fountain of Youth: The reverse-entropy universe in "The Counter-Clock Incident".
• Four-Fingered Hands: Spock, in a blooper in "Yesteryear".
• Freudian Trio: Just like the live-action version, we have Kirk, Spock, and McCoy.
• Friendless Background: "Yesteryear" lets us see Spock having this. His agemates torment him endlessly for being "a Terran" and Sarek, who expects his son to act like a Vulcan, is disappointed by Spock reacting to their teasing.
• Giant Flyer: "The Infinite Vulcan" and "The Eye of the Beholder" featured flying plant creatures called Swoopers.
• Girl's Night Out Episode: In "The Lorelei Signal", Uhura and Chapel have to lead an all-female rescue team due to the planet's inhabitants' ability to drain men of their Life Energy.
• God Guise: Keniclius 5 with the Phylosians in "The Infinite Vulcan", and Kukulkan by the ancient Mayans in "How Sharper than a Serpent's Tooth".
• Haunted Technology: The Enterprise computer gains a prankster personality in "The Practical Joker".
• Healing Hands: "The Infinite Vulcan". Spock's clone revives his original with a mind meld. Because of the difference in scale (the clone is a giant), he uses just one fingertip.
• High-Tech Hexagons: "Beyond the Farthest Star". The Enterprise crew discovers a highly advanced alien ship in orbit around a dead star. The alien ship's interior structure is made up of interlocking hexagons.
• Holodeck Malfunction: "The Practical Joker" includes a proto-holodeck in the Enterprise's rec room long before TNG's. McCoy, Uhura, and Sulu are trapped in it when the Enterprise computer gains a trickster mentality.
• Hollywood Psych: "Mudd's Passion" mixes up two types of love: friendship and eros.
• Human Aliens: Although there are still a fair few, this show takes advantage of the animated format to avert the trope whenever they can and come up with more divergent alien designs.
• Humanity on Trial: "The Magicks of Megas-Tu." Humanity is put on trial by the Megans, for the crime of being xenophobic jerks. The trial is actually for "humanity and those who would aid them" in order to account for the nonhuman crew members. Humanity initially has its sentence suspended because it is concluded that they do not pose a threat to the Megans since it is nearly impossible to locate the Megan homeworld. Humanity is found not guilty after Kirk risks his life to protect a Megan who had been sentenced to a Fate Worse than Death for associating with humanity. When asked why they didn't just use the Enterprise's records to discover for themselves that humans were capable of things like a Heroic Sacrifice, the Megans reply the records could have been faked.
• Improbably High I.Q.: The Lactrans in "The Eye of the Beholder". A six-year-old Lactran has an IQ in the thousands.
• In Space, Everyone Can See Your Face: Life-support belts take this to its logical extreme—the production team doesn't have to draw spacesuits, but can simply use its normal character models with a belt and a glowing outline.
• Indy Hat Roll: In "Once Upon a Planet", Kirk leaps through a sliding rock door in the side of a mountain just before it closes.
• Insectoid Aliens: The episode "Beyond The Farthest Star" has the Enterprise encounter an alien spacecraft orbiting a lifeless planet at the edge of the galaxy. Its organic shape resembles the chambers and tunnels of an ant colony, and its metal hull isn't rolled or cast, it's been drawn into filaments and spun like spider silk. When the landing party attains the ship's command section, they activate an Apocalyptic Log which shows the insectoid captain on a viewscreen.
• Instant A.I.: Just Add Water!: The planetary computer in "Once Upon a Planet" develops artificial intelligence on its own.
• Intelligent Gerbil: The Kzinti in "The Slaver Weapon", and the Caitian M'Ress.
• It Belongs in a Museum: Sulu in "The Slaver Weapon". Spock sets him straight.
• Just Between You and Me: In "The Jihad", after Charr is revealed as The Mole, he reveals his plan to start a holy war between his people, the Skorr, and the rest of the galaxy.
• The Ken Burns Effect: Just as the live action series would often come back from a commercial break to have Kirk deliver his "Captain's Log" to a stock shot of the Enterprise floating above the Planet of the Week, the animated series would have Kirk deliver the log as we slowly pan across a background painting of an exotic alien landscape.
• Life Drinker: "The Lorelei Signal". The women of the planet Taurus II drain the Life Energy of men to maintain their youth, causing Rapid Aging in the men.
• Limited Animation: Filmation's Signature Style. Lacking much range in facial expression, the onus was on the voice cast to convey the characters' emotions, which (being made up of mostly Original Series alumni) they largely succeeded.
• Losing Your Head: The title character in "Bem" has the ability to separate his body parts.
• Lost Colony: Terra Ten in "The Terratin Incident"... only it wasn't really lost—just shrunken to an extremely tiny size.
• Lotus-Eater Machine: In "How Sharper Than A Serpent's Tooth", the animals in Kukulkan's zoo believe that they are living in their natural environment, a hallucination generated by Kukulkan's machines.
• Louis Cypher: Lucien claims to have been Satan, in "The Magicks of Megas-Tu".
• Love Potion: "Mudd's Passion". Mudd himself thought it was Snake Oil, and is shocked to find out it works.
• Mage Species: "The Magicks of Megas-Tu" features aliens who are able to practice magic (unusual in a science fiction series).
• Meaningful Name: Bem, which means "Bug-Eyed Monster" in SF fandom.
• Mega Neko: The Kzinti in "The Slaver Weapon", as well as Lieutenant M'Ress.
• Merlin Sickness: Inhabitants of the alternate universe in "The Counter-Clock Incident" age backwards.
• Mobile Fishbowl: "The Ambergris Element". At the end of the episode, two Aquans (aliens who can only breathe water) are shown on the bridge of the Enterprise wearing water-filled helmets on their heads.
• The Mole: Charr in "The Jihad" reveals himself as the person behind the theft of the Soul of the Skorr.
• Morph Weapon: The titular device in "The Slaver Weapon" can turn into a a telescope, a personal rocket sled, a tiny computer, and an energy-beam weapon of a power never before seen. Among other things.
• Mr. Exposition: Ensign Walking Bear, a character never seen before or since, just happens to be on duty on the bridge at the proper moment to explain how Kukulkan is important in the history of his people, in "How Sharper than a Serpent's Tooth". Dawson Walking Bear (Comanche) was originally supposed to be in "The Patient Parasites". Fontana didn't really know what to do with him, but Russell Bates (Kiowa) included him in "How Sharper". He appears in three Star Trek: Phase Two fan film episodes. He is played by Wayne W. Johnson, who says he actually has no Native heritage.
• My Future Self and Me: Spock uses the Guardian of Forever to travel back in time and meet himself as a child in "Yesteryear."
• Mysterious Middle Initial: It was actually in this show that Kirk's middle name was first revealed to be Tiberius, though it wouldn't officially enter canon until the sixth film.
• Neglectful Precursors: The Slavers' stasis boxes.
• No MacGuffin, No Winner: In the end of "The Slaver Weapon", both the Starfleet personnel and the Kzinti renegades want to get the titular Lost Technology because of its awesome power: a beam that causes total conversion of matter into energy.
  Sulu: It would have looked nice in some museum.
  Spock: It never would have reached a museum, Lieutenant. There was too much power in that one setting. If not the Kzinti, the Klingons or some other species would have tried to possess it.
• Non-Malicious Monster: The Lactrans in "The Eye of the Beholder" put the crew of the Enterprise in a massive People Zoo, but Spock quickly catches on they legitimately are so intelligent they don't realize humans are sentient beings. They let the crew go once Kirk figures out how to communicate with them.
• No One Gets Left Behind: Kirk and Spock in "The Jihad" when the Vulcan gets thrown from a vehicle into the path of a lava flow.
• Novelization: All of the animated episodes were novelized by Alan Dean Foster for a series of books published as the Star Trek Log series, 10 in total. Initially, Foster adapted three storylines per book in novella format. The last few books, however, saw the writer take some of the 25-minute teleplays and expand them considerably into full-length standalone novels.
• Now Do It Again, Backwards: How the computer is repaired in "The Practical Joker"—Kirk tricks it into taking the Enterprise back through the Negative Space Wedgie the other way, by pretending to be scared of it.
• Ocean Punk: "The Ambergris Element" took place on the water world Argo.
• Opening Narration: An animated version of the one in Star Trek: The Original Series.
• Patchwork Map: Justified in "The Eye of the Beholder". On the planet Lactra VII the Enterprise crew finds deserts right next to forests, and Mr. Spock comments on how unnatural it is. It's eventually revealed that the alien Lactrans did it to make their planet a giant zoo.
• Patchwork World: In "The Eye of the Beholder", the planet Lactra VII had a series of different environments right next to each other, such as a desert next to a forest, each with appropriate animal and plant life. The Enterprise crew eventually discovered that they were deliberately created as part of an open air zoo.
• People Zoo: The Lactrans in "The Eye of the Beholder" capture the landing party and put them in their zoo.
• Planet Eater: "One of Our Planets Is Missing" features a space cloud that eats planets.
• Pleasure Planet: "Once Upon A Planet" featured the same planet that first appeared in the Star Trek TOS episode, "Shore Leave".
• Portal to the Past: The Guardian of Forever returns from the Original Series episode "The City on the Edge of Forever" to provide a portal to Vulcan's past in "Yesteryear".
• Power Perversion Potential: In "The Magicks of Megas-Tu," Sulu uses the magic of Megas-Tu's plane of existence to summon a beautiful woman... who transforms into Lucien when he goes to make out with her.
• Precision F-Strike: A quite mild example from "The Magicks Of Megas-tu," when Asmodeus describes the Earth from where the Enterprise crew came as "hellish."
• Pre-emptive Declaration: In "Albatross", when a native from the planet that put McCoy on trial follows them.
  Kirk: Besides, he'll be sure to take advantage when he sees that we've carelessly left our shuttle bay door open.
  Uhura: But we didn't, sir.
  Kirk: Oh yes. See to that little oversight, will you, Mr. Sulu?
• Pretending to Be One's Own Relative: In the episode "Yesteryear", Spock goes back in time to his own childhood and pretends to be a cousin named Selek.
• Psychic Static: Used to defeat the Kzinti telepath in "The Slaver Weapon".
• The Quest: The hunt for the "Soul of Alar" artifact in "The Jihad".
• Rapid Aging: What the Life Energy draining by the women of Taurus II does to men in "The Lorelei Signal".
• Real Men Wear Pink: The Klingons in "The Practical Joker" and the Kzinti in "The Slaver Weapon", courtesy of a colorblind director.
• Reality Is Out to Lunch: The planet Megas-Tu in "The Magicks of Megas-Tu" is in a part of the universe where reality breaks down. One character has their arm break off of their body and drift away.
• Reality Warper: The inhabitants of the title planet in "The Magicks of Megas-Tu" can bring anything into existence with but a thought. While they were on Earth they were considered to be witches and magicians due to their powers.
• Recycled Soundtrack: Well, duh, it's Filmation. While yes, this was also done on The Original Series, it definitely wasn't to the same extent.
• Replacement Goldfish: Carter Winston (actually a shape shifting alien).
• Ret-Gone: Spock in "Yesteryear" is temporarily Ret Gone until he creates a Stable Time Loop preventing his death as a child.
• Ripple-Effect-Proof Memory: Only Spock and Kirk remember the original timeline in "Yesteryear".
• Rite of Passage: The Vulcan kahs-wan in "Yesteryear", an ordeal in which Vulcan children must survive in the desert for 10 days by themselves with no supplies to prove their courage and strength. For young Spock, it becomes even more when his companion sehlat, I-Chaya, who had followed him against his wishes, was mortally wounded and the attending vet could only give Spock two choices, an extended life in agony or putting him out of his misery; Spock made the mature and logical choice to put him down.
• Robo Speak: Any computer voice done by James Doohan.
• Sequel Episode: "Mudd's Passion" is a sequel to "I, Mudd", "More Tribbles, More Troubles" is a sequel to "The Trouble with Tribbles", "Yesteryear" is a sequel to "The City on the Edge of Forever", and "Once Upon a Planet" is a sequel to "Shore Leave".
• Sdrawkcab Name: The retlaw plant in "The Infinite Vulcan" (named after Walter Koenig, the episode's author), and the planet Arret in "The Counter-Clock Incident".
• Sealed Evil in a Can:
  • "Beyond The Farthest Star". An evil Energy Being is trapped in a 300 million year old starship orbiting a black hole.
  • Played with by the eponymous weapon in "The Slaver Weapon". Spock and Sulu discuss the potential for such a weapon to destabilize the entire galaxy if it were to fall in to the wrong hands; however, the weapon is self-aware to the extent that it can determine that it's not being handled by an authorized user and self-destructs when the Kzinti try to activate it.
• Secret Test: "The Magicks of Megas-Tu". The Megans test the Enterprise crew to verify their good intentions.
• Self-Destructing Security: "The Slaver Weapon". The title device tricks the Kzinti into using a self-destruct setting to destroy it—and them.
• Self-Guarding Phlebotinum: In the episode "The Jihad", the Soul of the Skorr is protected by a force field.
• Shoot the Dog: Young Spock is forced to make this choice in "Yesteryear" when his pet sehlat, I-Chaya, takes an attack for him. The local healer tells him that he can save I-Chaya, but the creature's venom would leave him in constant pain. Spock chooses the Mercy Kill.
• Sickeningly Sweethearts: Spock behaves this way toward Nurse Chapel for a large part of "Mudd's Passion", because he's reacting to a Love Potion.
• Single-Biome Planet: A Volcano Planet in "The Jihad", an Ice Planet in "The Slaver Weapon" and a Water Planet in "The Ambergris Element".
• Snake Oil Salesman:
  • Harry Mudd in "Mudd's Passion", though he is unaware that the Love Potion he's peddling actually works.
  • Cyrano Jones in "More Tribbles, More Troubles" tries to convince the Enterprise crew that his new breed of tribble is harmless, without the Explosive Breeder properties of the original. (Instead, they grow so large, they eventually explode into a pile of tribbles anyway).
• Space Pirates: "The Pirates of Orion", complete with a pirate spaceship
• Starfish Aliens: Edosians, Vendorians, Phylosians, Lactrans, and M/3/Green. The production team was clearly thrilled to not have to worry about budget constraints when designing the aliens, to the point that they probably went overboard with it. (Also, if the aliens naturally fly, swim, or slither, you don't have to animate them walking.)
• Steal the Surroundings: In "The Terratin Incident", an entire miniaturized city is beamed aboard the Enterprise in order quickly to save the inhabitants from impending doom.
• Stock Sound Effects: Aside from the time it once used a Godzilla roar, it also replaced the typical red alert with the one from a single episode of the show this spun-off from.
• Swiss-Army Weapon / Talking Weapon: "The Slaver Weapon" has the titular device. It can function as a communicator, a laser, an energy-absorber, a ballistic weapon, a monosword, and has a total conversion setting. It even tells the K'zinti pirates which setting is its most powerful. (Too bad this was a Batman Gambit.)
• Tie-In Novel: Alan Dean Foster wrote adaptations of the episodes, and many Trek novels reference it.
• Temporal Paradox: "Yesteryear" revolves around a Reverse Grandfather Paradox in which Spock prevents his own death as a child. He doesn't do it quite right this time around, resulting in a slightly revised timeline when he gets home. Originally, his pet had lived. This time, he arrives a moment late, and the pet dies.
• The Time Traveller's Dilemma: It's unknown what happens to Thelen the Andorian (who replaced Spock as Science Officer) after the timeline is fixed in "Yesteryear".
• There Is No Kill Like Overkill: "The Slaver Weapon", a hand weapon capable of generating a Hiroshima-like detonation complete with shockwave!
• Title: The Adaptation: As noted, however, this is only the case for the re-releases. It originally aired just as "Star Trek," with no subtitle.
• Trap Is the Only Option: Hints of this in "The Pirates of Orion". McCoy and Scotty are suspicious when the Orion captain asks Kirk to beam down to an asteroid to get the medicine he and his crew stole. Kirk agrees that it's dangerous, but he also knows that "without it, Spock doesn't have a chance."
• 20 Minutes into the Future: Thanks to a blooper involving the mustached Lt Kyle, one shot of Scotty working the transporter momentarily showed him with a mustache, five years before his live action mustache's debut in Star Trek: The Motion Picture.
• Two of Your Earth Minutes: "The Lorelei Signal". Every 27 years, a starship is lured to a planet where female aliens drain the Life Energy of the male crew members. While explaining the situation to Lieutenant Uhura:
  Head Female Theela: To survive we must vitalize each 27 years of your time.
• Vengeful Vending Machine: "The Practical Joker". After the Enterprise passes through a mysterious energy field, the ship's computer starts playing practical jokes on the crew. When Scotty tries to obtain a sandwich from the food synthesizer, it sprays food all over him, including a custard Pie in the Face.
• "Well Done, Son" Guy: In "Yesteryear" Spock wants to prove to his father Sarek that he is a true Vulcan by undergoing the Kahs-wan Rite of Passage.
• Who Wants to Live Forever?: In "The Lorelei Signal", the women of the second planet of the Taurean system neither age nor die. However, any men on the planet die quickly. They must lure humanoid males to their planet once every 27 years and drain them of their Life Energy in order to survive. They can't escape their planet and they can't even have children.
• Winged Humanoid: The Skorr, a race of bird-people who were the the focus of the episode "The Jihad".
• Wise Serpent: How Sharper Than A Serpents Tooth" has the Enterprise encounter a starship shaped like a winged serpent. This alien ship is piloted by an actual winged serpent named Kukulkan, who visited Earth thousands of years earlier. Kukulkan guided the early Mayans out of tribalism, and into civilization and academia. He's pleased that his name and legacy are remembered, but still regards humans as childlike: inept and immature, still needing his guidance.
• Wizard Duel: Kirk takes on Asmodeus, the leader of the Megans in "The Magicks of Megas-Tu" despite being hopelessly outclasssed.
• World of Chaos: The planet in "The Magicks of Megas-Tu", and the so-called "Mad Planet" in "The Jihad".
• Wrongly Accused: In "Albatross", McCoy is falsely accused of indirectly killing people of a plague they weren't cured of.
• Year Outside, Hour Inside: This occurs in the titular area in "The Time Trap".
• You Are in Command Now: Lt. Uhura in "The Lorelei Signal", something which never happened on the live-action show.
• You Can See That, Right?: Kirk to Spock in "The Time Trap" when the Klingon battlecruiser disappears.
• You Won't Feel a Thing!: In the episode "The Pirates of Orion"...
  McCoy: [about to give an injection] This won't hurt a bit, Spock.
  Spock: An unnecessary assurance, doctor, in addition to being untrue.
  McCoy: That's the last time I waste my bedside manner on a Vulcan.