Plot-Relevant Age-Up

A character is aged, usually to adolescence, after being in another dimension, time travel, or other application of phlebotinum, often to get a main character's kid to "speaking age" or otherwise build them up to be able to take part in that world's adventures. Often done with clones (which would normally be born as infants), to age them up to fight the main cast. Done for the same functional reasons as the inexplicable age up in sitcoms, and easily spotted in advance if the presence of a baby or little kid doesn't make sense in the long run.

Often the reason this happens, as opposed to simply bringing in an older character in the first place, is writers want to use use some kind of girl-is-pregnant storyline, but aren't willing to wait the eighteen or so years before the baby becomes interesting. Common if the child is The Chosen One.

Occasionally, the writers will decide the age-up was a mistake (or won't be able to hold onto the age-up actor), and will revert the character back to where they started.

Differs from Soap Opera Rapid Aging Syndrome in that there is an actual in-story explanation, regardless of its believability, for the rapid maturation of the character.

Sometimes, especially for female characters, there may be some events similar to She's All Grown Up.

A Sub-Trope of Overnight Age-Up. See also Time Skip, where it's the show that jumps ahead, not a character.

Anime

 * In Gunbuster, they make use of a more or less realistic interpretation of time dilation as they get closer to the speed of light. This resulted in one of the characters going from sixteen to mid-40's while the main heroine, Noriko Takaya, aged a mere year or two.
 * In RahXephon,
 * Hotaru in the final season of Sailor Moon, after suffering a plot-relevant age-down more than a season before.
 * Chibi Usa also goes through this when Wiseman transforms her into the Dark Magical Girl villainess Black Lady. She is healed at the end of Sailormoon R and becomes a child again. It then happens again in both the manga's Dream Arc and a single episode of the SuperS anime, where she and Usagi actually swapped ages. The anime and the manga have different reasons and solutions for this problem.
 * Soukou no Strain has enough Techno Babble about sub-lightspeed travel that you never know just how old anybody is, although they all feel the age that they appear to be.
 * Also happens to Chris Thorndyke in Sonic X. Unfortunately when he travels to Sonic's world an inconvenient time warp sticks him back in his twelve year old body. This left the audience dealing with a more mature and useful Chris while keeping his more familiar body, making it easier for animators who had been drawing him as twelve for a couple of years now. There were certainly fewer complaints about him afterwards.
 * Hana-chan does this in the first episode of Ojamajo Doremi Dokkan, turning from a baby to an 11-year-old girl.
 * In Magic Knight Rayearth, Ascot ages fast with sheer willpower because of a crush on the significantly older Umi. Having a entire world run on willpower can be useful sometimes.
 * Subverted in Pretty Sammy. Washu's Dangerous Drink turns Sasami into a sexy teenager, but only for a short while: by the next day, it has backfired, and she's become a toddler. When Washu does the same thing to Pixy Misa, the result is a battle between (probably) the youngest pair of magical girls in the genre.
 * Vivio, near the end of Magical Girl Lyrical Nanoha StrikerS. ; presumably she couldn't access her powers as a child. She eventually reverts to her younger form,
 * When she gets older, she gets the ability to switch to "adult mode" at will.
 * , formerly, of Bleach
 * After some rigorous offscreen training in the dangai, where time passes exorbitantly fast,  returns looking all grown up.
 * Mahou Sensei Negima has pills that allow one to increase or decrease your age at will. They see quite a lot of use.
 * There's also a more subtle version going on in regard to Negi's constant use of various Year Inside, Hour Outside items; he's aged himself up by at least a year, if not more, in less than six months. It mirrors his ever-growing maturity.
 * Instead of 8 year old Futa also being involved in the Future Arc, his 18 year old self stays to be a competent supporting cast. Doesn't happen with Lambo and I-pin, though.
 * In Dragon Ball, Piccolo grows from a small child to an adult in a span of three years, probably because it would be a little strange for Goku to fight a little kid who wants to take over the world.
 * This is made even more obvious by the fact that Goku himself doesn't age at all until a Time Skip that is setting up the next series.
 * Kon from Amatsuki spends two years in the virtual world before his classmate Toki arrives there, allowing him to grow into a Big Brother Mentor figure for the latter.

Comic Books

 * Marvel really has a lot of these:
 * Illyana "Magik" Rasputin of New Mutants went from five to fifteen in the middle of a rescue attempt, due to a time rate differential between Earth and the hell-dimension in which she was trapped.
 * The same happened to Marrow, only with her place being a pocket dimension called "The Hill".
 * Fellow X-character Nathan Christopher Summers is sent into the future as a baby and later comes back (roughly the same age as his grandfather) as Cable. Of course, he came back before he left, so at one point, both Adult Cable and Baby Cable were around at the same time.
 * And now we have Cable's protegee, Hope. It involves a lot of different futures.
 * From X-Factor: 's barelylegalification has her going to the future and coming back.
 * For a while even Reed and Sue Richards' son Franklin fell victim to this trope, being kidnapped into the future and coming back as the teenage Psi-Lord. Silly, yes, but it did give young Franklin's tremendous mental powers a break from Deus Ex Machina and/or Puberty Superpower duty - his older self was in control of them. It was, of course, later reversed.
 * Captain America (comics)'s Arch Enemy the Red Skull used his Deus Ex Machina to age his daughter Daddy's Little Villain Sin from a 13 year old Creepy Child Enfant Terrible into a 23 year old Axe Crazy Dark Action Girl that makes her father look sane by comparison.
 * The Hulk's sons Skaar and Hiro-Kala are physically young teens, but chronologically only a couple of years old, partly thanks to their mother being one of the alien Shadow People, who have an accelerated maturation rate. Skaar actually has a "puny" (human) form that is at least still a child.
 * When you consider Skaar's the first Hulk "person" to grow up from birth on-screen, his growth, muscle tone and mental development rate may be the norm. To give reference, in Son of Hulk #1 even as a newborn Skaar appeared to be nearly as large as one of Miek and the Brood's offspring and stronger than them.
 * Alexander Luthor, Jr. in Crisis on Infinite Earths.
 * Right before the Sonic Adventure arc of the Archie comics, Amy Rose does this to herself with a wish to justify her joining the party; otherwise, the rest of the gang would've forbidden her from joining for being too young, and the whole game tie-in thing would fall apart.
 * Apparently the same thing happened to her negative-dimension counterpart, Rosy Rascal, although her reasons for wanting to be older weren't quite so noble. It had the side effect of breaking her brain, turning her into a dangerous psychopath. And you thought Amy was possessive...
 * Arisia from Green Lantern physically ages herself from about 13 Earth years to at least 18 Earth years so she can pursue a crush on Hal Jordan. Later, to make Hal Jordan not look like a skeeve, this was subject to several Retcons, and, in current continuity, 13 years on her world are equivalent to 240 on Earth.
 * Jenny Quantum of The Authority does this to herself. After meeting the incarnations of centuries past and becoming aware of the current problem, Jenny uses her quantum powers to go from six years old to high school age.
 * Infinite Crisis did this to Bart Allen/Kid Flash via spending four years in an alternate dimension accessed via the Speed Force, thus turning him into someone old enough to be the new Flash (after spending a while, Refusing The Call) while Wally and his family were on another planet. He was then the new Flash for a while
 * Interestingly, the reason Wally was off on the other world was to deal with his speed-powered twin kids who were receiving the same treatment- they're chronologically less than two but look eight or so, so they're being rushed into the Family Business.
 * Gold Digger has Brianna, an accidental composite clone of Brittany and Gina. She was born fully grown, with both sets of memories, and had to establish an identity for herself. It was eventually established that some of her more childish personality traits owe to the fact that her soul is still her real, chronological age, and never got to experience a real childhood. Her granny was the only person insightful enough to treat her with the level of affection she would give a little girl.
 * While the Phantom Zone normally suspends aging, Superman's son Chris emerges from its imprisonment as a teenager.
 * The Mighty Thor inverted this, giving Loki a Plot Relevant Age Down where he was reincarnated as his child self after dying. It avoided being Narm or too heavy-handed when an echo of the older Loki revealed his reasons for having it happen. Preteen Loki has been hugely popular, making it work very well.

Film

 * Saphira in the film version of Eragon. In the span of exactly one minute, she goes from a cute baby/child dragon to a fully grown adult capable of speaking telepathically (in an audibly adult female voice) and carrying Eragon on her back. This effect comes complete with flashing lights, sound effects, and a generous smoke screen to hide the actual transformation.
 * Eragon blessed a baby who grows to about four years old in her next appearance. It turns out he actually cursed her, forcing her to eat huge amounts of food, making her mature mentally and physically at a rate far faster than normal. It Makes Sense in Context.
 * In Warlock the titular Evil Sorcerer cursed the heroine to age by 20 years each day just For the Evulz. However, she managed to reverse the spell and restore her youth.
 * In The Return of Hanuman, Hanuman reincarnated as Maruti rapidly ages into an elementary school student in three months in order to quickly help an elementary school boy from being bullied.
 * In Excalibur, Morgana ages her son Mordred from a child to a young adult in order to face Arthur in combat.

Literature

 * Used in Douglas Adams' novel Mostly Harmless; Trillian's daughter Random goes into an intergalactic daycare as a preteen and comes out past puberty. It turns out the daycare was also temporally displaced, and the time you come back is random.
 * This is the main plot of William Sleator's Singularity. One twin locks himself inside a Year Inside, Hour Outside device, so that he'll be a year older than his twin and thus no longer a twin.
 * Inverted in the Discworld novel Wyrd Sisters. A three-year-old Rightful King is useless, but an 18-year-old Lost Prince is generally pretty reliable when it comes to overthrowing the Usurper. So the titular witches send the Prince away, then move the entire kingdom 15 years into the future, so the people won't have to suffer under the mad duke.
 * In the last of Piers Anthony's Apprentice Adept books Wunderkinds Flach and Nepe age a decade between chapters..
 * In The Gap Series by Stephen R Donaldson, Davies Hyland is force-grown from a fetus to a 16 year old teen. Of course, he's also implanted with the mind of his 22 year old mother.
 * In Cordwainer Smith's story The Dead Lady of Clown Town the major character D'joan (later Joan) is force-grown from age five to age sixteen in one night.
 * In the Magic: The Gathering book Legions, the reincarnated Kuberr grows up in the course of a few weeks. Justified in that he is a reborn god (of wealth no less) born of Phage and the Patriarch who are basically incarnates of death themselves) and is actually growing at a rate that corresponds to the number of deaths in the world, while a war is going on.
 * In the Animorphs companion and backstory book "The Andalite Chronicles", Loren ages from about 13 to around 18 in the course of a few minutes after a botched attempt at using the Time Matrix strands them in a weird, mixed reality: at the center is a time paradox, explained with lots of Techno Babble, that basically runs much faster than normal. They have to enter here to regain the Time Matrix and travel back home. Loren uses it's ability to hedge the details of reality to make sure nobody at home notices, either.
 * In 'the Snow Queen' by Hans Christian Andersen, the main character Gerda, rescues her friend from the snow queen after being inflicted by a shard of the devils mirror and turning cruel and cold hearted. But when they arrive back home in there garden they turn to find themselves both adults. Poetically the whole adventure portrayed their adolescence.
 * In the Doctor Who Virgin New Adventures, teenage Action Girl Ace gets betrayed by the Doctor one too many times, and leaves him. Four books later, the Doctor arrives in almost the same time period, and cynical twentysomething mercenary Ace rejoins the TARDIS crew.
 * Star Trek: New Frontier does this to Xy, the son of Burgoyne and Selar. In the three-year gap between Stone and Anvil and After the Fall, he goes from young toddler to science officer. The reason is that the combination of Vulcan and Hermat DNA makes him age super-fast...but it also means that he'll die before either of his parents.
 * The first year in the mill in Krabat counts as three. Becomes important because at the beginning of the story, Krabat was too young to be interested in girls (and he needs a girl to defeat the villain). Justified by magic.
 * About a third of the way through Jerry Ahern's Survivalist series, the Earth's atmosphere catches fire (don't ask; it's nonsensical but awesome). John Rourke and his family and two best friends have managed to gain possession of some suspended animation booths, and go to sleep for the estimated 500 years it will take for the oxygen level of the atmosphere to recover sufficiently. Unbeknownst to the others, John sets his booth to wake him up about twenty years early. When he discovers that there's enough air to get by Denver-style, he wakes up his 8- and 6-year-old children, spends a few years teaching them survival basics, and then goes back to sleep himself for another decade-and-a-half. Then all the adults wake up as scheduled to find that the kids are suddenly twenty years older than they remember (Mom, in particular, is pissed). John doesn't attempt to dress up the fact that he did this in order to make their little group into three possible breeding pairs rather than the two it would have been (no, not the siblings; the daughter with the other adult male and the son with the other adult female), just in case it turned out they were the only surviving humans. They weren't, but it was a very pragmatic plan, and the predicted couples did end up together eventually anyway.
 * In H.P. Lovecraft's The Dunwich Horror, Wilbur Whateley grows to young adulthood within five years of his birth.
 * In Time Scout run to Denver, then to London. They show up in London a few hours before they leave for Denver, three years older. Tragic, as it means that
 * In Darke, the sixth book of Septimus Heap, Jenna and Septimus have gone from 12 years in the preceding book Syren to 14 years, where he will have to have the Darke Week.

Live-Action TV

 * Angel
 * In season 3 when Angel's son was born, kidnapped, sucked into another dimension where time moves faster, he comes back as a 16 year old.
 * Also used when Buffy apparently kills Angel, but actually sends him to a hell dimension at the end of season 2. When he returns months later in Season 3, he is actually several centuries older. Of course, being an immortal vampire, he looks exactly the same. His mind, on the other hand...
 * Percy goes from a teenager to an adult in between the two seasons of Starhunter, despite supposedly being trapped where she couldn't age at all. This is likely due to Dawson Casting: Percy was played by 25-year-old Tanya Allen, and, since the second season was filmed 3 years later, couldn't pass for a teenager anymore.
 * Isabelle in The 4400, later doing the reverse and temporarily de-aging for plot relevant reasons.
 * Star Trek, from The Next Generation on, uses this a lot, almost always in the form of using Bizarre Alien Biology to Hand Wave Soap Opera Rapid Aging Syndrome:
 * Star Trek: Deep Space Nine actually did a one-shot of this trope, where the O'Brien's toddler daughter Molly is aged to adolescence by some Applied Phlebotinum. Thankfully, they find a way to make her young again by the end of the episode.
 * They also did this with Worf's son Alexander, justifying it by establishing that Klingon children mature very fast. Alexander was played by several different actors and always behaved about as old as he looked. Deep Space Nine really pushed it by making him physically and mentally a young adult at the chronological age of, oh, seven. (The fast aging is especially odd if you consider that Klingons also live longer than humans, a fact established so Klingons from The Original Series could show up.)
 * This troper had a good Fridge Logic explanation for why Klingons live so long. Klingon medical tech expressly ignores things like surgery or any procedure that would otherwise save a warrior dying from battle wounds. This is because Klingons believe that dying in battle is an awesome thing that should be devoutly wished for and that dying of natural causes is viewed the same way Catholicism views suicide (an abhorrent one-way ticket to hell). Therefore the Klingons must have developed some kind of medical technology to keep their warriors healthy and able to fight well into old age so that they retained a chance to die an honourable death in battle. A natural side effect of this is that their lifespans would also be increased.
 * And to anyone who says Klingons wouldn't stoop to genetic manipulation to taint their natural form, remember the smooth forehead incident...
 * This also may be a natural factor: Q'onos was probably an extremely harsh world where infant mortality might be extremely high due to natural predators, etc. Klingons living longer and retaining their strength and vigor into old age, thus being fertile for much longer in their lifespan might have been a natural adaptation to keep the species alive. It would also explain their extremely short maturity period.
 * Klingons aren't alone in this, by the way. The most extreme example is Voyager's Kes, whose race has a nine-year lifespan. In one alternate future episode, Kes had a daughter with Tom Paris ... and that daughter was old enough to marry Harry Kim within a year or two.
 * Deep Space 9 also has the Jem'Hadar, who age incredibly fast b/c of special genetic modifications.
 * Voyager also has Naomi Wildman who is ½ Human - ½ Ktarian. At age 2 chronologically, she looks and acts like an 8-year-old Human. Like Alexander, this is handwaved that she's half an alien.
 * Another Star Trek: The Next Generation example: At the start of season two, Troi goes from newly pregnant to having a baby in a few days. The kid then grows from babyhood to about ten years old in a similar space of time, before "dying".  This was actually one of the first episodes to really cement Troi's position on the show and make her something other than a walking plot device to read minds. This may be explained, however, by the fact that the episode was one of those originally written for Star Trek: Phase II before that series was scrapped and replaced by the first movie. The original script centered around Lt. Ilia.
 * In the final season of Stargate SG-1, cast-member Vala gives birth to Adria, who is introduced as a plot point. Adria is an engineered leader of the bad guys who grows to adulthood in just a handful of episodes.
 * Adult character Teal'c was also aged to middle age for his species due to Time Travel. He had to go back in time to prevent the problem they'd spent the last fifty years on, so his change is for keeps, carrying over to The Ark of Truth and his Stargate Atlantis guest appearance.
 * There was also the episode where Jack O'Neill was aged to geezer status... by a nanotech STD, no less!
 * Power Rangers SPD: child villain Mora is turned into adult villain Morgana... which turns out to have been her true form all along. But she prefers being a child and gets herself changed back.
 * Happens more than once during Xena: Warrior Princess:
 * Gabrielle's daughter Hope does so and becomes her mother's Evil Twin.
 * Inverted later when Xena and Gabrielle go to sleep for thirty years in coffins of ice and awake to find Xena's daughter Eve has aged to adulthood.
 * Examine the case of Walt from Lost: he began the series as a 10 year-old. However, because the first three years of the show covered only the last three months of 2004, actor Malcolm David Kelley quickly grew older than his character. Thus the character was written out in season 2. When the series time-jumped three years after the rescue of the Oceanic 6, Walt returned in a few appearances, having aged appropriately. However, in the season 3 finale, Walt appears to Locke in December 2004, looking as the actor did in 2007. This appearance was referred to in-show as "taller ghost Walt."
 * Arguably this is what happened to Trance in the second season of Andromeda, where her future self convinced her younger self to trade places in time. At one point in a later season she mentions that she misses being as young as she once was. Of course since she's actually the avatar of a missing sun, she qualifies as Really 700 Million Years Old.
 * One of the more Egregious examples is V, in which Elizabeth goes from newborn to toddler to sexually active teen in record time.
 * Ultraman Mebius takes place 20 years "real time" after the last monster attacked and brings back everyone except Taro's actor.
 * In Hex, Malachi does this, going from an infant to a teenager in a year, due to being half-demon.
 * Used in Doctor Who; The newly regenerated Doctor meets the little girl Amelia Pond, who asks to travel in the TARDIS, and the Doctor accepts. Of course, having a little girl around in a show where there's usually at least one death every episode would be a bit dark - and besides, a eight-year-old can't do Fan Service. So having the Doctor accidentally jump 12 years into the future means that we can now have an all-grown-up Amy travel with him.
 * Doctor Who also has the fastest age-up yet seen.
 * In V-2009, Ryan's daughter is aged up from a baby to a 7-year-old because she is used to test the rapid aging treatment that is used for Lisa's replacement.
 * The original V did this with Elizabeth (twice!), supposedly because of her Half-Human Hybrid status.
 * from Earth: Final Conflict grows from a newborn to adulthood during the first part of the first episode of the second season. Explained by his being alien.
 * The West Wing has an Inversion: when Zoey Bartlet was introduced in the first season, she was stated to be 19. In season 2 they decided that she was actually 17 so to add drama to the MS storyline.

Video Games

 * In Final Fantasy IV, Rydia, a young girl when the party first encounters her, is swallowed by the Leviathan and carried into the Eidolons' land of Feymarch. When she is reunited with the party, presumably no more than a few weeks later, she has aged into her early twenties because time passes much more quickly in the Feymarch.
 * Notably, when you actually travel there, you don't get any older.
 * If only because you don't normally stay there for very long like Rydia did. And with the time flow different between the two areas, when you spend some considerable amount of time in the Feymarch, mere minutes pass by outside by the time you leave.
 * Ran in Twinkle Star Sprites ages to somewhere past puberty when she powers up and becomes Princess Sprites..
 * Metal Gear-verse clones age normally up until the time when senescence starts to set in, which then hits them like a train. This was used to age the main character, Snake, from a young and handsome hero in his early thirties into an Older and Wiser forty-something in the space of only two years in chronology. In Metal Gear Solid 4, despite the fact that he is chronologically in his early forties, he is, by all appearances and genetic testing well into his seventies. Heck, he looks older than some eighty year olds in the game. Prior to this, Snake and Raiden had seen how hard the aging hits with Solidus Snake in Metal Gear Solid 2—despite being chronologically younger than Solid Snake, the Patriots had engaged his accelerated aging process early so that he would appear to be middle-aged during the events of the first game and thus By the time of the game's events, Solidus's accelerated aging has gone even further and he rather resembles Snake in Metal Gear Solid 4.
 * In Shadow Hearts: From the New World, Johnny ages-up when in a late-game transformation form.
 * In Super Marisa Land (A Touhou version of Super Mario), Marisa starts as a toddler but ages up and down depending on how many power ups she has.
 * The Bizarre Adventures of Woodruff and the Schnibble starts with Woodruff, a toddler, aging into an adult after his adoptive father Azimuth sticks a device on his head. This device turns out to be
 * In the Warcraft universe, the young archmage Khadgar vanquished his close friend turned Fallen Hero Medivh by magical means, and in the process suffered a one-off curse that caused him to prematurely age. By the time adventurers re-discover him in the Burning Crusade expansion, he is chronologically in his late 30s or early 40s but physically much older.
 * In the Sengoku Basara series, Ieyasu goes from a Bratty Half-Pint in the second game to a rather beefy teen in the third game. Particularly unusual in that all other returning characters remain completely physically unchanged.
 * In Xenogears we have Esmeralda. At first she has the appearence of a 10-year-old girl. But after doing a certain Sidequest, she gets the appearance of a 20-year-old woman.

Web Comics

 * El Goonish Shive has the unusual situation of
 * Also in EGS, the inability to rapidly age the Lycanthropes plays a part small but important in Grace's Backstory.
 * Happens twice in a loudly lampshaded manner in PvP with Francis and Marcy, the first time with some Fourth Wall Breaking and the second revealing questionable rules of ageing for the webcomic's world. Technically, they should have already been at that age anyway, but rather than draw them aging in a natural manner from strip to strip, the artist opted to update them all in one shot.
 * It also has something to do with Brent's prediction of  way back when the comic was still comedic.
 * In The Inexplicable Adventures of Bob, Molly, Galatea, and Djali are species that age from babyhood to vague teenagerdom in the span of one month.
 * Done repeatedly and then reversed in The Wotch to Evan/Lily. It's not actually relevant to the plot a lot of the time, but it has been used for a few story lines.
 * from One Question.
 * One of the many effects of the Timey-Wimey Ball in Enjuhneer is that characters stay the same age for an entire year, then suddenly change in a manner comparative to levelling up. This can cause drastic effects, or can be as simple as suddenly acquiring a pair of White Gloves with no idea where they came from.

Web Original

 * Sarah Swanson of Erika's New Perfume goes from three to sixteen complete with Fake Memories. Only her two once-older sisters Erika and Marie remember her ever being younger.

Western Animation

 * Lion-o from Thundercats, due to stasis failure.
 * Enzo and AndrAIa from Re Boot age from children into adults while trapped inside a game due to time flowing faster there.
 * Then the writers missed the young Enzo. So they cloned him and made the copy younger.
 * from Transformers Animated
 * The Tweebs in the fourth season of Kim Possible are an interesting variation: although their art makes them look older, they are not acknowledged as such, but merely advance-placed into Kim's high school during the Post Script Season).
 * Professor Farnsworth had his crew go out and get "chronotons" for the purpose of doing this to a team of super-mutant babies in Futurama.
 * At the end of the second season of Adventure Time, is reverted to age 13. In the second season episode "Too Young"  has to age back to eighteen years old in order to .  tells Finn that  always had the means to age up, but was having too much fun being a child again.