Explosive Breeder

"Baris: There must be thousands of them!

Kirk: Hundreds of thousands.

Spock: One million, seven hundred seventy-one thousand, five hundred sixty-one. That's assuming one tribble, multiplying with an average litter of ten, producing a new generation every twelve hours over a period of three days--

Kirk: And that's assuming that they got here three days ago--

Spock: Also allowing for the amount of grain consumed and the volume of the storage compartment--"

- Star Trek the Original Series

A creature which reproduces at an alarmingly fast rate. Often, there will be only one to start with, suggesting that it can reproduce asexually. If not asexual, the creature may employ Face Full of Alien Wingwong to extend its list of potential mates to outside its species or employ Express Delivery to bring on the next generation immediately. In extreme cases, there may be more total weight of offspring after a few generations than there was weight of available food. Which is completely impossible.

Often the real reason to fear a Ridiculously Cute Critter, Small Annoying Creature, or a Killer Rabbit.

Compare Mook Maker. Contrast Endangered Species.

Advertising

 * A Visa commercial showed a man buying a pair of rabbits for his daughter. After the man fills out a check, the pet store owner takes so long to verify it, the rabbits "get busy". The pet store gradually overflows with their offspring.

Anime and Manga

 * The man-eating rabbits in Pet Shop of Horrors.
 * Yu-Gi-Oh: Early on, Kuriboh's main strength comes from its ability to multiply into the thousands in the course of a single turn, allowing them to swamp even the most powerful opponents with self-destruct attacks.
 * Bio Meat: The titular creatures. Unfortunately for everyone, they're also Extreme Omnivores.
 * Digimon: In the second movie, the villain replicates himself several million times in just a few minutes. This is justified in that he's on the internet, and is explained as being a type of virus. Furthermore, the copies don't have nearly the same resistance to damage that the original does, as a Spam Attack destroys everything except the original.
 * Scarfies in Kirby of the Stars

Card Games

 * There are a lot of things like this in Magic the Gathering, although the ones that spring to mind immediately are the Slivers, the Eldrazi, and this.

Comic Books

 * A human example is Mother of Champions from DC Comics. Her power is to conceive a litter of 25 children each time she has sex, who complete gestation in 3 days, after which she gives birth. These metahuman offspring are superhumanly strong, but age ten years for each day they're alive, so they are used as expendable cannon fodder by the Chinese government -- she has no contact with them once they are born. She has apparently given birth to thousands of these offspring, sports a perpetual pregnant belly, and relies on a robotic chair with six insectile legs to carry her around, as she gets too large to walk on her own.
 * Myth Adventures: In Phil Foglio's comic adaptation, there's a Running Gag about small dragons that reproduce on contact with water. One of them happens to get into a market stall demonstrating umbrellas, and after that they keep showing up everywhere, until at the end of the scene the original owners are forced to round them all up. (The artist added even more dragons when the comic was reprinted as a graphic novel.)
 * Garfield: Played with in an early strip, in which the eponymous cat tosses a pair of coat hangers into an empty closet. It only takes until the end of the same 'strip for them to multiply until they fill the closet to bursting.
 * Coat hangers? There is a joke he was probably not trying to make there...
 * An issue of Star Trek: Alien Spotlight focuses on tribbles. In this version, they are at least semi-intelligent, and use their breeding offensively. There's also the implication that their breeding caused some sort of disaster, possibly due to lack of resources. And they did the breeding in response to Klingons ("rufflefurs") threatening the humans that showed up.

Film

 * Tron: The Grid Bugs.
 * Sammael in Hellboy reproduces two copies of itself for each one that's killed.
 * Evolution.
 * The... host-thing in Slither. Literal explosion, too.
 * The Crites in the Critters sequel were also rapid breeders.
 * Gremlins: The Mogwai/Gremlins. Don't get them wet.
 * In Godzilla, the species of the mutant lizard was capable of laying up to two hundred eggs asexually, threatening to replace humans as the dominant species on Earth..
 * Alien series: The Xenomorphs. Give the queen somewhere cozy and warm and she'll carpet it with eggs.
 * A literal Explosive Breeder, in fact.
 * Tremors: Shriekers, the second stage of Graboid life-cycle are this.
 * This applies to Dracula and his 3 brides in 2004's Van Helsing, who have laid hundreds of vampire egg sacks and try to find any living creature suitabl to revive them. The first attempt with a werewolf failed as the newly hatched baby vampires exploded during their short lives attacking a nearby village, while the second attempt with Frankenstein's monster was a sucess for the second batch of vampires (presumably laid right after the first batch died).

Literature

 * The guinea pigs in the short story "Pigs is Pigs" by Ellis Parker Butler (and the Disney cartoon adaptation).
 * Truth in Television. Guinea pigs are rodents, and will breed like mice given half a chance. This is why getting the sex of guinea pigs correctly identified before housing them together is important.
 * The Mote In God's Eye examines this in detail with the Moties; not only do they breed rapidly, they're biologically unable to avoid breeding. Their race has been destroying itself in apocalyptic wars and rebuilding from the ashes of their world for hundreds of thousands of years.
 * In David Eddings' The Elenium, the insect-like Seekers would, if permitted, cover the Earth with their eggs and feed all life to their offspring.
 * Fragment: One reason the island organisms pose such a danger to the global ecosystem is that they're all this trope.
 * Ringworld: City Builders are extremely fertile, such that every act of mating within their species automatically results in offspring. Females also go into heat periodically, making abstinence all but impossible for them. They consciously subvert this trope by mating with other sorts of hominid.
 * Henry Huggins: One of the books in Beverly Cleary's series has Henry buy a pair of guppies, only for the guppies to breed until his room is covered in fishbowls and feeding fish takes up all of his free time.
 * The Rolling Stones by Robert Heinlein: Martian Flat Cats. One flat cat produces a litter of eight kittens every thirty days or so. Not so bad comparatively, unless you're on the spacegoing equivalent of a RV and your trip lasts almost six months.
 * The Gryphons in The Wayfarer Redemption were born pregnant - with nine more Gryphons. Gorgrael's advisor intended them to only breed for three generations (Giving a total of 820 Gryphons), but Gorgrael found a way to make it self-sustaining. Since he kept the pregnant generation away from the front lines until they gave birth, getting rid of them was a serious problem for the heroes.

Live Action TV
""There's these two here... And those two there! How did that happen?""
 * Star Trek: The most famous example is the tribbles, which did mention that they reproduce asexually. In fact, they are actually born pregnant, and as long as they're fed, they'll keep making more tribbles. Word of God states that the tribbles were based on the rabbits in Australia . It's probably a good thing the Klingons and tribbles instinctively hate each other, since otherwise they would have wiped out all life on several planets. Nuking their homeworld was probably a bit much. "Do they still sing songs about the Great Tribble Hunt?"
 * Sanctuary: The Nubbins. Basically tribbles with eyes and teeth, plus the ability to become mostly invisible. Oh, and they're sexually juiced up from lots and lots of pheromones, which also affect humans.
 * In an episode of Father Ted, Dougal got a pet rabbit, and promises Ted he'll be careful with it. Cut to a week later, and there are rabbits all over the room, and neither Ted nor Dougal even notice.
 * On a season-finale episode of Hoarders, a Truth in Television example played out for a man who'd let his three pet rats -- one male, two females -- escape from their cage months earlier. He didn't have the heart to let them starve, or to separate the females from the litters they'd hidden in the walls, so just kept putting down food for them. Result? A ruined house from which over three thousand fancy rats were removed by humane-society workers.
 * The Nanites, on Mystery Science Theater 3000.
 * The Basil Brush Show used this as a Running Gag. In one episode. They bought two rabbits. However as the scenes pass, more and more appear.

Mythology

 * Echidna, Mother of Monsters. Many adaptations (Dungeons and Dragons for example) record her as the Ur-Monster, the ancestor of a large portion of the world's monstrous population... usually the near-mindless sorts, leaving the semi-humanoid or otherwise intelligent monstrous races to have been created by their own patron deities or whatever.

Video Games

 * Moria, Angband, and other related Roguelikes have several mostly low-level monsters which, as the in-game descriptions say, "can breed explosively." The most notorious of these are the worm masses, in all their annoying color variants. Even worse is in ADOM, where creatures get stronger as you kill more of them.
 * Dwarf Fortress has cats, which can actually breed so fast that if you dump a bunch into they will still breed faster than they are killed. Their, ah, fruitfulness, would not be a problem by itself, as only a very few animals need to eat yet and cats aren't one of them -- so they're an infinite source of meat and leather, if you don't mind violating conservation of matter. However, unlike most animals, cats adopt their owners, and once this happens, they can't be butchered, and killing them in some other, completely unintentional fashion will give their pet dwarf a bad thought. Keeping them, on the other hand, will wreak havoc on your framerate -- and of course, they'll breed more kittens.
 * The massive framerate issues from an uncontrolled cat population has been nicknamed a "catsplosion".
 * Since the latest batch of updates, poultry and rabbits have been added to the animals dwarves can keep.
 * Rabbits actually have some form of population control-- they need to graze on grass or fungus in a pasture, or they'll starve to death. Despite this, "releasing" them into cavern pastures full of fungus has had the expected results of rabbits breeding faster than they could be killed by wildlife, and on occasion even killing particularly puny Forgotten Beasts.
 * Poultry on the other hand do not require food yet, they lay and incubate eggs in large clutches, and it is theoretically possible to surpass the population cap many times over by having forty female turkeys (a dozen or so eggs per clutch) and one male, and enough nestboxes for a massive birdsplosion.
 * Space Monkeys in Space Quest V. They actually exploded a space station they were in.
 * One of Knights of the Old Republic's sidequests has the player dealing with an invasion of gizka -- small cute critters with an exponential breeding rate that are basically the Star Wars counterpart to tribbles -- on their ship. They're apparently considered pests on many worlds and many different traders in the game stock gizka poison.
 * Ratchet and Clank Going Commando: The Protopets. They also reproduce asexually by spitting their offspring fully formed from their mouths. If you miss even one of a group of them, they will do just that the second you turn your back, often ending up with more than there were originally. It's no wonder that.
 * Diablo 2: Some of the beetles, particularly the ones in hell, however, they don't have fast maturing rates, and the kids act much differently then the parents in terms of attack plans, making it more of a Mook Maker.
 * Halo:
 * The Flood. The carrier forms literally explode to disperse infection forms. The infection forms also mutate their hosts implausibly fast. The Flood are like a macro-scopic version of The Virus.
 * The Grunts. Their homeworld is a Death World where natural flame geysers are but one hazard among many. One way the Grunts cope with this as a species is by breeding very rapidly. When taken out of that environment, they have to be given contraceptive chemicals in their food and breathing gas to keep their population growth manageable. However, these restrictions are lifted in times of serious war when the Covenant need more light infantry.
 * Quest for Glory: The antwerp in is a literal Explosive Breeder.
 * Cerebus' in God of War could spit out Cerebus Seeds, nasty little puppies that would grow into full-grown Cerebus', and spit out more Seeds... One mini-boss fight in the game was basically trying to kill a small group of them before you got overwhelmed.
 * The Palm OS game Space Trader has the Tribbles. Woe betide you if you're carrying food goods while they're on your ship. If you can find the tribble collector, though, you could sell them off for some serious credits.
 * The Gonarch in Half-Life, also qualifying as a Mook Maker. Apparently the final stage in the life cycle of Headcrabs, it is essentially an enormous quadrapedal exoskeleton with an equally enormous testicle dangling from it, from which it spawns an endless amount of underdeveloped Headcrabs until Gordon kills it.
 * Unholy War: The Prana Devils. Their out of battle ability is to produce another prana unit. In battle, they lay eggs with hatch into baby pranas that chase the opponent.
 * The krogan of Mass Effect used to be this trope in order to withstand their Death World home planet. Scanning one former krogan colony world showed that they reached critical overpopulation in one generation. If it weren't for the genophage, they could easily have overrun the galaxy. The genophage reduces them to one live birth in a thousand (the rest being stillborn). If they didn't kill each other so fast this would leave them with fairly stable population growth rate.
 * There are also Pyjacks, which are much like the Gizka before them in KOTOR. These were formerly called "space monkeys" in Mass Effect 1 and have become a major pest on the Krogan homeworld.
 * Starcraft: The Zerg Rush. In fact, their gameplay mechanics are based around in producing millions and millions of little creatures.
 * Here's a fun experiment: Take any two compatible Pokémon, and leave them at the Day Care. Once you have your egg, time how long it takes for the next one to appear. Repeat ad nauseum.
 * If one of them has a different Trainer ID (was traded for), but they're both the same species, breeding will go insanely fast, and the Day Care owners will even comment that they seem to like each other a lot.
 * In Epic Mickey, Oswald the rabbit has 420 Bunny Children. They're adorable and eat mooks.
 * In BIOMETAL, a computer analysis apparently shows the titular monsters increasing in such a number that, if their planet is not destroyed within 32 hours, they would take over the entire galaxy!
 * Creatures: Norns. Especially a genetic variant known as Fast-ager norns, who reach adulthood within seconds, live forever and are incredibly fertile. Many Fast-ager norns also go through pregnancy extremely fast, leaving them ready to breed almost immediately. If it weren't for the population limit preventing new eggs from hatching, they'd crash your game.
 * In Galactic Civilizations, the Torians and custom races with the same Super Ability breed four times as fast when they're happy. This tends to cause morale problems due to overpopulation, but on the other hand boosts your income (more people = more taxpayers) and makes it hard to invade your worlds unless the enemy has Spore Ships.
 * The Minecraft rabbits mod allows two rabbits to breed a baby rabbit when placed in close proximity. The issue it that this gets going exponentially when put in a small enough space:
 * In The Guardian Legend, one of the enemies in the labyrinth areas is a blue spider that if left unkilled, turns orange, then red, then it splits into seven identical copies of itself. These individual copies can split even more, making things a little... complicated.

Web Original

 * Chakona Space has the Faleshkarti, when they reach maturity they become obsessed with sex, sex triggers a hormone that decreases their intelligence, and the only way to slow the hormone's progression is to get pregnant. Also, they're Hermaphrodites so every single one of them can give birth. When the Federation makes contact with them every inch of land on their homeworld is covered with arcologies and the oceans had been converted into massive algae farms.

Western Animation
"Johnny: I told you bunnies would take over the world! And they have!"
 * Rabbits and rodents tend to show this trope. Truth in Television -- but often comically exaggerated.
 * Rugrats has a pair of gerbils exploding into a huge, seething gerbil-sea in the basement in the space of two weeks.
 * Ed, Edd 'n' Eddy: a pair of rabbits reproduced so quickly that they filled a garage to bursting within a few hours. It did not help that Ed was allergic to rabbits. It Got Worse. The entire cul-de-sac was overshadowed by a tsunami made entirely of rabbits.

""And the males have started laying eggs!""
 * One Tex Avery cartoon has two rabbits conjured on a singer's arms produce about six bunnies in the time it takes him to hide said arms behind his back (about a second).
 * Another Tex Avery cartoon (based on the Fairy Tale The Elves And the Shoemaker) shows some elves towing a long rolling tray with two bunny slippers on the front of it. It goes behind a pillar, and when it comes out the other side, the tray is covered in tiny bunny slippers.
 * A commercial pokes fun at the length of credit card verification by having a pair of rabbits a girl and her father bought multiply exponentially.
 * The Naughty Naughty Pets took this to an utterly insane level, having rabbits literally pop out of thin air. The entire planet was coated with them after about two minutes.
 * The Disney short Pigs is Pigs has this with guinea pigs. We start with two and by the end of the short there's well over a million. When two go out of view temporarily, expect at least three kids to show up when they come back into sight.
 * An idea for an Oswald the Lucky Rabbit short had Oswald being overwhelmed by the never-ending influx of bunny children, even going as far to attack the stork.
 * Epic Mickey: Oswald The Lucky Rabbit has 420 kids. His mate? Ortensia, a cat.
 * The Partridge Family in 2200 A.D. had Rubi-roobian Rubits, which were mostly a Shout-Out to Tribbles.
 * Futurama: Started happening to penguins.


 * Happened when Bender duplicates himself creating two smaller Benders and they duplicate themselves and so on. They multiply and become smaller until they are atom sized and infest the Earth.
 * The Simpsons : Bull Frogs were depicted as this when Bart, ignorant of the purpose of quarantine laws, brought one with him when the family went to Australia.
 * Whatever Chowder and Panini are, as they resemble rabbits. In the flash-forward finale, Panini has had fifty babies, twenty of which she had popped out the previous day.
 * The Smurfs had fuzzles, which multiplied whenever they ate something.
 * The Angry Beavers: The beavers decide to stay up all night because they're not tired. After a night of shenanigans and fun, they find themselves still not tired so they use various methods, including using a herd of sheep to sleep, to no avail. However little did they know the power of their alarm clock was off, leaving it the same time. They realize they have been awake for thousands of years when they find their house in the middle of a futuristic world over-populated entirely with sheep.
 * My Little Pony Friendship Is Magic: The Parasprites from "Swarm of the Century". Like the famous tribbles, they also reproduce asexually and end up eating everything.
 * The Jakovasaurs on South Park. The two that are the last of their kind breed and children keep popping out. When the town tries to get rid of them with a fixed game show, the prize is a trip to France for himself and 50 of his closest relatives.
 * Oddly inverted with St. Peter Rabbit, who apparently had just one descendent (Snowball) despite being of this trope's archetypal species.

Real Life

 * Truth in Television for many, many animals. These animals tend to be lower on the food chain, so most of their offspring get eaten. That's why the planet hasn't been overrun yet. Moving one of these species to a new habitat that lacks their natural enemies, though, is a bad idea. Case in point: rabbits and mice in Australia.
 * Some microorganisms have a gestation period measured in minutes. Which is why they mutate so fast. What takes the average macroorganism (maturity at four years) to evolve -- say, seventy generations for it to be well entrenched and spread through the population -- takes the average bacterium one day. Finish your antibiotics.
 * To give you an idea of just how fast bacteria populations can grow if unrestricted, if it takes ten minutes for one bacterium to become two, then in an hour you will have sixty-four. In five hours you will have one billion. In twenty-four hours you will have 2.2 times 10^43--about one hundred times the mass of the entire Earth! In forty-eight hours they will have exceeded the mass of the visible universe. Most micro-organisms reach stationary phase due to space or food shortages, or environmental pressure, long before this happens.
 * Many invertebrates facilitate this trope by breeding parthenogenetically, eliminating the delay imposed when a mate must be located. Aphids and rotifers are probably the best-known examples of this.
 * Aphids even go one step further than not needing to mate to get pregnant, they are actually born pregnant.
 * Ignorant human fishermen inadvertently invoke this trope when they cut starfish in half, thinking they're eliminating the competition for mussels and oysters. Too bad the pieces of a bisected starfish can regenerate, creating two hungry echinoderms...
 * Internal parasites must invoke this trope in spades, as only a tiny fraction of their eggs or larvae will be lucky enough to make it into a new host organism. Tapeworms, the uber-example, are basically a continuous strand of gonads with an anchor at one end.
 * All mites are born with a half dozen embryos already inside of them.
 * Their extremely short reproduction cycle is one of several reasons why Drosophila melanogaster (fruit flies) are very useful as model organisms, e.g. for genetic experiments.
 * In population biology, "k-selected" species are limited by competition for resources in their environment, which is why they invest heavily in a few offspring to insure their survival. "r-selected" species are in environments which allow rapid population expansion (e.g., flowers in spring time). They have as many offspring as possible but invest little to insure individual children's survival. The "Explosive Breeder" is r-selected.