That's Miri. She looks great considering she's centuries old.
Original air date: October 27, 1966
The Enterprise answers a distress beacon from a planet that seems to be a carbon copy of Earth. No one answers their hails, so they beam down to investigate. What they find looks like downtown Detroit on a bad day. As Bones forlornly inspects a decaying tricycle, a strange person covered in blue lesions attacks him. The person cries over the broken trike after being wrestled into submission. And then he dies. Further searching brings them to a building where a young girl named Miri (Kim Darby) has been hiding in a closet. She tells the landing crew about the "Grups" who all got sick and killed each other. Even the animals died, leaving the "Onlies", children of pre-pubescent age.
Soon after, Kirk realizes he has a blue lesion on his hand. They have to find a way to cure the disease, to save themselves and all the Onlies. Unfortunately, their communicators have been stolen by Miri's friend Jahn, the little bast—uh, scamp!
Troperi:
- Actor Allusion: Janice Rand says she always wanted Kirk to notice her legs. The Starfleet costumes went from sensible slacks in the second pilot ("Where No Man Has Gone Before") to miniskirts solely because Grace Lee Whitney complained they were hiding her "dancer's legs".
- Adult Hater: The Onlies are violently suspicious of all adults who they refer too as "Grups".
- Artistic License – Physics:
- A planet that is an identical copy of Earth, right down to the same positions of the continents. Despite this startling and very implausible discovery, the planet doesn't have much relevance to the plot itself.
- When James Blish wrote the novelization of the episode, he changed the planet to being a long lost human colony that lost contact with Earth, and not an identical copy. The plot of the story largely remained the same. He was likely working from early drafts of the script.
- And in the book Forgotten History, it's explained as being a displaced Earth from an alternate timeline that ended up in the main timeline somehow.
- The Before Times: The Trope Namer, in regards to the times before The Virus killed all of the adults.
- Big "NO!": Shouted by Rand when she realizes she has lesions, too. Miri also when Kirk points out one on her arm.
- Blah, Blah, Blah: Used by the children as a stock response whenever any of the crew tries to tell them something.
- Cobweb of Disuse: Spock and Kirk pull the hospital files (as in, manila envelopes) out of 300 years of cobwebs. Did the disease spare the spiders?
- Continuity Nod: To "The Enemy Within", as Kirk is deeply uneasy being alone with a crying Janice, and awkwardly pats her on the back in a crappy version of a hug.
- Creepy Child/Enfant Terrible: The Onlies, even if they're Really 700 Years Old.
- Creepy Children Singing: Combined with Mocking Sing-Song.
- Creepy Doll: One hangs in the window of the building where the Onlies hang out.
- Depopulation Bomb: A genetic engineering project got out of hand and killed off everyone over puberty. The children are still around, because the intended effect of the project was to drastically slow the rate of aging and it worked fine on anyone it didn't kill, at least till you reach puberty.
- Disaster Scavengers: How the children have survived for over 300 years. Kirk and his team note that the surviving canned goods are starting to run short and that the children will soon starve to death unless they intervene.
- Emotional Maturity Is Physical Maturity: The locals not only look like children, but act like children, despite being many times older than Kirk or his friends.
- Fiery Redhead: Jahn, the little ginger brat!
- Future Slang: Adults are "Grups" (a corruption of "grown up") and children are "Onlies" because they're the only living beings left. "Foolie" is a violent game with about as much structure as Calvin Ball.
- Ghost City: The place where Kirk and crew first beam down.
- Green-Eyed Monster: Miri betrays Kirk to the other Onlies after she sees Kirk give Rand a comforting hug.
- Growing Up Sucks: Especially when it means you're gonna die.
- Hand Wave: An infamous one. The concept of an alternate version of Earth existing elsewhere in the galaxy is invented just to explain why the outdoors scenes were filmed on the Desilu Productions backlot.
- Hate Plague: The disease causes its victims to be progressively short-tempered, culminating in outright violence.
- Held Gaze: Kirk and Spock held each others' gaze for a full twelve seconds, in complete silence, as the camera flicked back and forth between closeups of their faces, after engaging in extremely flirty dialogue.
- Hero Antagonist: Jahn. Annoying little brat though he may be, he had every reason to suspect the landing party’s motives and to assume that they would be just as much of a threat to the Onlies as all the other Grups had been, and that they needed to protect themselves. Had McCoy not managed to find a cure in time, he would have been right (it would have been somewhat academic by then, as the Onlies would have run out of food within months, but Jahn didn't know that either).
- He Who Fights Monsters: The children accused their adult overlords of violence. Then they inflict violence on Kirk and make him bleed, and he proceeds to point this out.
- Immortal Immaturity: The Onlies still act like children despite being hundreds of years old.
- Long-Lived: Due to the effect of a life-prolonging virus, the children are three hundred years old.
- Mocking Sing-Song: The Onlies are fond of annoying Kirk and co. with the standard "Nyah Nyah!"
- Mysterious Waif: The eponymous Miri.
- Never Land: The episode contains a fairly dark example: a planet of long-lived, unaging children who sicken and die upon reaching long-delayed adolescence.
- Nightmare Face: The face of anyone who is in the last stages of the fatal disease.
- Older Than They Look: The children on Miri's planet are all much older than they look, with Miri herself being over 300 years old in 2266.
- Only Fatal to Adults: The plague doesn't affect children; Spock theorizes that the changes involved in puberty are a factor in susceptibility.
- The Plague: The disease that killed all the adults.
- Precocious Crush: Miri has one on Kirk. He tells her she's pretty, but he may be flattering her in order to get her to be more co-operative.
- Professor Guinea Pig: Our heroes are trapped on a planet and slowly dying from a disease that kills all adults. The McCoy has mixed up what may very well be the antidote. Only problem is, he's not sure, and the only way to be sure is to check the Enterprise's computers, which can't be done because the local Creepy Children have stolen the communicators. What to do? Why, wait until Spock leaves and inject yourself, of course!
- Really 700 Years Old: Miri appears to be a chestless 12-and-a-half-year-old. Actually, she's at least 300 years old.
- Red Shirt: Averted; not only do the two in the episode survive to the end, but they don't even get visibly sick.
- Rules of Orphan Economics: The Onlies have been living out of the supplies left by the original colony for three hundred years. Captain Kirk tells them they would not be able to survive much longer this way, because the food's running out. Some fans speculate that they could have made it a while longer. Many children are capable of learning to take care of themselves, and space colonists would have emphasized this. Learning how to plant and grow food in gardens would have been a big deal; they would even have had books on it, and older kids would have taught younger ones to do this. Whether they'd have the patience to do so, however...
- Selective Obliviousness: When Kirk tries to convince Miri that every single one of the Onlies will eventually catch the disease and turn into a feral Grup, she desperately insists that it only happens "sometimes". Kirk manages to get through to her by pointing out the blotches that have begun appearing on her own skin.
- Shaming the Mob: ...is easy when they're all emotionally under 13. Kirk pointed out that he was hurt and bleeding and it's their fault. They've become no better than the Grups who murdered each other.
- Staring Kid: When the Onlies gang up on Kirk, one girl in a green wig just stares dispassionately.
- Still Wearing the Old Colors: Jahn wears an army jacket. Given his age, it's unlikely he was in any branch of the (now obviously defunct) military.
- Surprisingly Realistic Outcome: Everyone warns Kirk that manipulating a three hundred year old childlike girl entering puberty will end badly and with her thinking she's in love with him. And it does, despite him thinking she just wants comfort, she's upset when she sees him (awkwardly) hugging Janice, betraying him to the other kids and scornfully calling him "Mr Lovey Dovey".
- Technicolor Science: The laboratory where McCoy studies the virus includes an elaborate set of tubes containing a bubbling blue liquid with no apparent purpose beyond adding visual interest.
- Teenage Wasteland: A planet where a virus had killed off all the adults, leaving the children to look after themselves.
- There Are No Adults: See above.
- Typhoid Mary: Due to his Bizarre Alien Biology, Spock cannot be infected by the disease but he can carry it.
- Transatlantic Equivalent: Really cool coincidence: Two days after the airing of this episode, over in Great Britain Doctor Who would air the fourth episode of "The Tenth Planet", a serial that featured a twin-planet of Earth and one of the main characters dying of a slow-acting disease.
- Voodoo Shark: We need a disease on a distant planet that largely wiped the inhabitants out, and the disease also affects the human crew, and by the way we can't afford alien makeup for the survivors, because there are too many. So let's make said planet an exact duplicate of Earth, complete with human beings! Why is it exactly like Earth? Because LOOK OVER THERE! (The novelization makes this decision seem even dumber by using an obvious alternative reason: it's a lost human colony.)
- For that matter, Star Trek has frequently used stock sets and background locations without bothering with such an explanation; just because the buildings and rocks generally look like Earth buildings and rocks doesn't mean the entire planet has to have the exact same geography as Earth.
- We Will Not Have Pockets in the Future: Not made explicit, but affects the plot in its own way. When the entire crew leaves to investigate a noise, their communicators are all left on tables, allowing them to be stolen. Actually a point in Roddenberry's initial concept for the show; "A Starfleet officer should never be seen putting anything in his pockets," because they don't have any. Hence the use of velcro (standing in for a more futuristic technology) to attach things to people's belts.
- What Happened to the Mouse?: A big mouse, at that. The episode begins with the Enterprise crew making the astonishing discovery of a planet identical to Earth. They beam down to investigate, and get caught up in a plot about a plague that kills adults and leaves children alive. This presents a mystery and danger that is duly solved. The episode ends without any further mention of the fact that the planet is identical to Earth.
- Eventually explained, decades later, in reference materials. A Federation scientist studying this planet discovered that at some point in the past, the Sol system passed through a Negative Space Wedgie that caused the entire solar system to be duplicated at the subatomic level. One nearly perfect duplicate (this planet) was created near the center of the anomaly, while two less perfect duplicates (the planet featured in "The Omega Glory" and the 20th-century Roman planet in "Bread and Circuses") were created closer to the edges — the duplicates appearing out of subspace in different areas. All ended up diverging from Earth at different points in history, with the nearly perfect duplicate being identical to Earth until the mid 20th century. It should be noted that Voyager encountered a Negative Space Wedgie very similar to this, which resulted in near-perfect duplication of the ship. The presence of the anomalies actually explain "Hodgkin's Law of Parallel Planet Development" proposed in the original series.
