There are a lot of characters who can [[VoluntaryShapeshifting change their shape]]. Some have fewer options than others, and a lot are limited to only [[SwissArmyHero a handful of forms]]. One common set includes an aged pair: the same general appearance, in a childlike and an adolescent or adult form. Often, one will be the natural form for the character, with the other being [[InvoluntaryShapeshifting invoked by some external trigger]]. But most of the time, the child form will be used only to make the character look more innocuous or relatable.

See also OlderAlterEgo for a child who gets powers in adult form, and SleepModeSize for a powerful adult [[ShapeshifterModeLock Mode Locked]] into a child form. If the character just ages from childhood to adulthood by normal means, it's a PlotRelevantAgeUp or TimeSkip. If a child is forcibly transformed into an adult, it's OvernightAgeUp; the inverse is FountainOfYouth.

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!!Examples:

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[[folder: Anime & Manga ]]

* Signal in the manga/anime ''TwinSignal'' has two forms: An adult {{Bishonen}} form, and a childlike SuperDeformed mode with an insane [[TrademarkFavoriteFood love for chocolate.]]
* Mosquito from ''SoulEater'' can change his form back into several younger states of him self, each which excelled in a certain ability.
* [[spoiler: Walter C. Dornez]] from ''{{Hellsing}}'', after siding with Millenium and being a patient of the Doctor, is able to revert to the form and strength of his younger day.
* Miss Hinako in ''RanmaOneHalf'' has the default form of a girl of about eleven years, and turns into a [[HelloNurse curvaceous]] twenty-something by [[EnergyAbsorption absorbing]] LifeEnergy, {{Battle Aura}}s and KiAttacks. Although it's never addressed in the source material, it seems likely that her adult form is her true age, and her child form is the result of slowed aging due to Happosai giving her EnergyAbsorption powers via altering her metabolism with {{Pressure Point}}s.
** Happosai's old friend Rakkyosai is cursed to change into a small child after falling into the Spring of Drowned Boy. The thing is, he's exactly the same ([[MiniatureSeniorCitizens toddler-like]]) size in both forms, so he has no advantages or disadvantages from one body to the other, but his real body is more... ''wrinkly''. A lot more.
* In ''YuYuHakusho'', Koenma sometimes appears as a toddler and sometimes as a young man.
** There's also Genkai, who is, by default, [[NeverMessWithGranny an old lady who's also a martial arts master]], but rejuvenates to a young adult when using her Reiha (because it's a technique that, by spreading out the user's spiritual energy, changes them to how they looked when they were at the peak of their powers).
* Juugo from ''Manga/{{Naruto}}'' turns into a child when he gives Sasuke some of his flesh to heal him; he turns back into an adult after absorbing one of the samurais.
* In ''TenchiMuyo'', Ryo-Ohki is a shapeshifter with four forms: a spaceship, a "cabbit" (cat rabbit creature), and child and teenage humanoid forms- the last of which is hard for Ryo-Ohki to control or maintain. [[note]]The manga explains that a large part of the reason it's hard to control is physics- she doesn't know how to walk with that much weight suddenly added up top, and once she's practiced dealing with the raised center of gravity, she can use that mode fine.[[/note]]
** Also Washuu, who can take any form she pleases, but spends most of her time as a little girl.
* Nel in ''Manga/{{Bleach}}'' returns to her adult form by absorbing energy from attacks.
* Vivio and Einhart of ''Manga/MagicalGirlLyricalNanohaViVid'' both have their normal, elementary school forms, and their teenage forms they use in combat.
** [[spoiler:Curren Huckebein]] shows this ability in ''Manga/MagicalRecordLyricalNanohaForce''.
** Familiars such as Arf also have the ability to become either a child or an adult, in either their human or animal forms.
* Age misrepresentation pills in ''MahouSenseiNegima'', and whatever magic Eva uses. Mainly used for disguise, the only combat effect is the change in reach.
* ''Anime/SpacePirateMito'' is an alien that [[OlderThanTheyLook looks like a third grader,]] [[ReallySevenHundredYearsOld despite being over ten thousand years old]], but has a [[PowerArmor mail suit]] that she uses for combat that looks like an adult human. She has similar suits for [[MobileSuitHuman just masquerading as a human adult]], and a good deal of the conflict in the first half of the series comes from trying to get her half-human son to accept her actual, childlike, form, when for most of his life he's only seen her in mail-suit form.
* In ''Manga/AhMyGoddess'', Belldandy mentions that the three goddesses are each a representation of time. Belldandy represents the Present, so when she uses too much of her power, she just needs to sleep. However, when her sisters use too much power, Urd, representing the Past, reverts into a child form, while Skuld, representing the Future, grows up into a teenage form.
* In ''HellTeacherNube'', both Nube and [[TheRival Tamamo]] (extremely experienced spiritualists) can use astral projection to generate child-like bodies for themselves while their real ones lie in a sleep-like trance. Nobody ever seems to recognize them despite looking nearly identical to their adult forms (although Yukime thought child-Nube was exceedingly cute.)
* In ''Manga/HayateTheCombatButler'', Isumi's great-grandmother can take child form by drinking other people's blood; when the effect wears off, she reverts to her true form. Like Rakkyosai above, [[MiniatureSeniorCitizens there's not much difference between her two forms]], apart from her true form being really, ''really'' wrinkly.
* Jewelry Bonney of ''Manga/OnePiece'' does this. She could change her age to any other amount too. And does change the ages of others as well, as a combat technique. She and her crew wear undersized clothes, possibly so they become right-size when they're changed into kids as a disguise.
* The slightly obscure manga(?) ''1520'' has an interesting version of the trope. The two main characters, a 15 year old prince and a maid from opposing kingdoms, eat a magical cake by accident that transforms them into ten year old children. Whenever the maid laughs or the prince sheds a tear, that individual will return to their proper age, at the cost of de-aging the other down to about five.
* In Manga/MillenniumSnow, Yamimaru (the vampire's bat companion) can take on human form as either a strong young man or an adorable little boy.
* ''Anime/MacrossFrontier'' has Klan Klan, a Meltran who has a physical defect that causes her to regress in age when micronized to human size. When giant-sized, she's mature and... developed. When human-sized, she appears as (and acts like) a preteen.

[[/folder]]

[[folder: Comic Books ]]

* ''{{Shazam}}''. Ten year old Billy can transform into Captain Marvel by saying a magical word.
* ''{{Thunderbunny}}''. (Lesser-known 80s comic in which a boy transforms into a grownup anthro rabbit superhero).
* Skaar, one of [[Comicbook/TheIncredibleHulk the Hulk's]] sons, can change between a small gray child-like form, and a bigger Hulk-like form.
* Similar to [[IAmNotShazam Captain Marvel]], ComicBook/TheUltraverse's ''{{Prime}}''. He also had a DistaffCounterpart called "Elven".
* One of the ''Series/{{Heroes}}'' tie-in comics had The Russian, a [[DifferentlyPoweredIndividual Special]] who posed as an entire [[TheFamilyThatSlaysTogether crime family]] with his ability to physically age and de-age himself at will.

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[[folder: Film ]]

* Dave Bowman in ''[[Film/TwoThousandTenTheYearWeMakeContact 2010]]''.

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[[folder: Literature ]]

* Aphrael in ''TheElenium'' and the ''Tamuli''. Being a [[PhysicalGod goddess]], she can look however she wants, but generally takes child form because it makes her [[GodsNeedPrayerBadly easier to adore]].
* Foster from Keith Laumer's ''[[http://www.webscription.net/10.1125/Baen/0743488555/0743488555.htm A Trace of Memory]]'' goes from an old man to a youth in the space of an evening... but loses his memory in the process. It turns out this happens to him [[spoiler: indeed, his entire species]] on a regular basis. The plot is motivated by his friend's quest to restore Foster's memory, and TheReveal has to be seen to be believed: it's one of the cheekiest [[TomatoSurprise twist endings]] in all of literature - cleverly foreshadowed, but still quite shocking in its chutzpah.
* Hecate from ''TheSecretsOfTheImmortalNicholasFlamel'' goes from being [[TheHecateSisters a maiden in the morning, a mother during the day, and a crone by the evening]]. It should be noted that she does not have control over the process, however.
* The original ''Literature/{{Dracula}}'' appeared as an old man most of the time, but turned young if he had recently fed.
* In ''The Power of Six'' in the Lorien Legacies series, 7 meets up with [[spoiler:10]], whose first Legacy is to be either a 7-year old, her actual age, or a 17-year old.
* Feruchemists in ''Literature/{{Mistborn}}'' can store their age in the metal [[{{Unobtainium}} atium]], allowing them to shift to be as young or old as they want- but since Feruchemy is based on EquivalentExchange, they can't make themselves young without spending the same amount of time old, and vice versa, meaning this power is normally considered fairly worthless except for disguise purposes. [[spoiler: [[GodEmperor The Lord Ruler]], however, can do both Feruchemy and Allomancy, and by combining the two systems can get a ''lot'' more power from his Feruchemy, meaning that he essentially has eternal youth so long as he spends a few hours every few days as an old man]].

[[/folder]]

[[folder: Live Action TV ]]

* ''[[http://en.wikipedia.org/wiki/Big_John,_Little_John Big John, Little John]]'' -side effect of a sip from the FountainOfYouth.
* ''Series/PowerRangersTurbo'': Justin after transforming into a Ranger. Sometimes averted, when he doesn't wear his helmet. Justified because of the footage of [[Series/GekisouSentaiCarranger Carranger]].
** In ''Series/PowerRangersSPD'', there's Mora, who starts the series as a child, then partway through is transformed into an adult named Morgana (which is actually her natural form), before being turned back into Mora near the end.
* Kibaranger in ''Series/GoseiSentaiDairanger'' does things the same way as Justin.

[[/folder]]

[[folder: Video Games ]]

* Link in ''VideoGame/TheLegendOfZeldaOcarinaOfTime'', by way of TimeTravel. Also [[spoiler:Midna]] in ''[[VideoGame/TheLegendOfZeldaTwilightPrincess Twilight Princess]]'', who spends most of the game in SleepModeSize.
* [[spoiler: Mithos/Yggdrasil]] from the game ''VideoGame/TalesOfSymphonia''.
* The titular ''VideoGame/SpaceAce'' in the laserdisc video game is turned into a child as a result of the BigBad Borf's "Infanto Ray". During certain parts of the game, the player has the chance to "energize" Ace and turn him back to his adult form for a short time; adult Ace sequences tended to be more about fighting villains while child Ace spent most of his time trying to avoid or escape enemy attack.
* [[spoiler:Misha]] of ArTonelico became a child when she lost the [[MagicMusic Chronicle]] [[MacGuffin Key]]. [[spoiler: You can later change her age at will by adding or removing Chronicle Key]]
* Pollin, the MagicalGirl parody from ''VideoGame/TechRomancer'' has her standard "little girl" mode and occasional older version.

[[/folder]]

[[folder: Webcomics ]]

* 21 year old [[http://wiki.thewotch.com/E_Onymous Evan Onymous]] of ''Webcomic/TheWotch'' can transform into a 4-year old girl called Lily ("Lil E"). (Also a fully-grown female version, Missy ("Miss E").)
* Pandora from ''Webcomic/ElGoonishShive'' appears in her child form when she reveals herself to mortals, and assumes her adult form when dealing with her son and during her later appearances in the ephemeral universe parallel to the physical plane of existence called the spiritual plane. These are not her only forms however; as a [[VoluntaryShapeshifting shapeshifter]] she can appear as anything between [[SuperSmoke a monstrous "cloud"]] and a clone of any other character.
** Mr. Raven can alternate between a sixtyish form and a twentysomething one.

[[/folder]]

[[folder: Western Animation ]]

* Clockwork from ''WesternAnimation/DannyPhantom'' constantly shifts between different ages due to his time-related powers.
* Subverted with one ''WesternAnimation/DextersLaboratory'' episode where Dexter and Deedee plan to become adults in order to watch an R-rated movie. By mistake, Deedee knocked over the wires of the aging machine, then re-plug them in the opposite sockets, causing the machine to go sour, [[FountainOfYouth turning everyone into babies]], leaving Dexter and Deedee's ages unchanged.
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