History Main / ShapeshifterBaggage

* No attempt is made to explain how the BigBad of ''Film/{{Guyver}}'' is able to turn from a middle-aged CorruptCorporateExecutive in a suit into a room-sized monster. Most other Zoanoids only become slightly larger than humans.

* In ''WesternAnimation/TurningRed'', giant red panda forms seem to mass proportionate to their size. Mei's seems as much as a large bear, most of her female relatives' seem as much as elephants or more and Ming's seems as much as a blue whale.

* Abused to hell and back in ''White Knight, Grey Queen'' where Tonks not only repeatedly changes into forms ranging from a small child to a 400-lb. man during the Final Battle but does it ''within seconds''. Plus she somehow mysteriously ''gains the skills and abilities'' of the more specialized forms, like when she morphs into an "Oriental gymnast" and can suddenly do fancy twirls and stuff.

* ''ComicBook/SpiderMan'''s Doctor Connors regrows his arm whenever he becomes the Lizard. When this transformation happens gradually it can be {{handwave}}d; growing it back was, after all, the point of his research. But then there's Komodo, whose improved version of the Connors' formula lets her shift between forms at will. In human form, she hasn't got any legs, and it becomes a bit harder to rationalize someone losing and growing back their legs as a result of falling asleep on a plane for a few minutes.

* Although it is explicitly stated that ComicBook/PlasticMan cannot change his amount of mass, he at one point shape-shifts to [[http://upload.wikimedia.org/wikipedia/en/0/0c/JLA_89_coverart.jpg the size of a building,]] while apparently remaining dense enough to fight a similarly-sized ComicBook/MartianManhunter and smash through concrete.
* ''[[ComicBook/TheIncredibleHulk The Hulk]]'':

* ''Franchise/SpiderMan'''s Doctor Connors regrows his arm whenever he becomes the Lizard. When this transformation happens gradually it can be {{handwave}}d; growing it back was, after all, the point of his research. But then there's Komodo, whose improved version of the Connors' formula lets her shift between forms at will. In human form, she hasn't got any legs, and it becomes a bit harder to rationalize someone losing and growing back their legs as a result of falling asleep on a plane for a few minutes.

* ''ComicBook/NewMutants'': [[Characters/NewMutants Warlock]] seems to have no limit on how large he can transform (and change his mass to fit the size) instantly, but for some reason he doesn't really transform into anything smaller than he originally was.

* [[ComicBook/MsMarvel2014 Ms. Marvel]]'s ability to shapeshift and change size is eventually explained as working by shunting her mass back and forth along her timestream to when she needs it.

* ''WebAnimation/StrongBadEmail'' discusses this at length in [[https://www.youtube.com/watch?v=yeGS-cojKA4 episode 192]].

** Where did [[Characters/XMenTheOriginalTeam Beast]]'s fur go when he walked near Jimmy/Leech? (''Days of Future Past'' gave kind of a HandWave by having younger Beast going from "regular human" to "blue cat person" through a serum, so Beast's fur could have retracted into his hand)

** Averted in the novelization of ''Film/X2XMenUnited'', where Characters/{{Mystique}} reflects that she's good enough that she makes it looks easy -- even though it's not. If she wants to grow in size significantly, she has to gain mass; if she wants to shrink significantly, she has to lose mass; and she always has to keep in mind the position of her organs. Based on the comics (unless this changed recently); unlike other shapeshifters, Mystique can't change mass and has to keep a generally human form. It's even suggested that she can remain in her Raven Darkholme form indefinitely because there's no change in mass, while trying to keep the same mass in a larger form is a strain that keeps her from using such forms for long. Given her [[ReallySevenHundredYearsOld age and experience]], however, that sort of 'strain' is a relative term. In her solo series of comics, she demonstrated an incredible creativity with the use of her powers despite the limits she had compared to most other shapeshifters. Among the feats she performs is flattening out to avoid taking damage by an explosion, [[OneWingedAngel assuming a monstrous form]] by ''sprouting a second face and pair of arms'' in order to quadruple wield (though she specifically mentions that doing so was ''very'' dangerous to her health, brain, and a massive strain to her powers), faking a glass vial being broken in her hand, faking the effects of a lethal virus, smuggling items in a "flesh pocket" in her stomach, and pointing out that since she mimics all her clothing too, she's {{technically naked|Shapeshifter}} all the time.

* In ''TabletopGame/DungeonsAndDragons'', the various VoluntaryShapeshifting and ForcedTransformation spells and abilities ignore conservation of mass, as demonstrated by 125-ton dragons {{Humanshifting}} into standard-size humanoids. Some editions explain this as magic drawing energy and material from the [[ElementsOfNature elemental Planes]] to fuel their effects.

*** The novelization explains that it can't turn into a small animal like a rabbit but can turn into a group of rabbits linked by a HiveMind that can't go far from eachother. Also they're able to use hologram shells to imitate clothes but not functioning objects like Osgood's inhaler.

[[folder:Webcomics]]
* In ''Webcomic/CatNine'', Myan can transform into smaller or bigger animals (or a cat girl) without any problem because of her magic collar.
* In ''Webcomic/HolidayWars'', AprilFoolsDay is a shapeshifter whose limitation is that his mass always stays the same. UsefulNotes/LaborDay explains this in [[http://www.holiday-wars.com/blog/2010/09/03/episode-48/ this strip]].
* Averted in ''Webcomic/{{Digger}}'': After turning into a huge monster, Shadowchild points out that in that shape it is stretched out thin and can't do much besides looking scary, and this is with Shadowchild being not exactly solid, but presumably magical, to begin with.
* ''Webcomic/ElGoonishShive'' starts off with a human shapeshifter who can change her density, but not her mass. Then people start getting zapped with ultratech alien devices that don't obey conservation of energy, magic is brought in, and the whole thing breaks down.
** Somewhat justified, in that despite the [[AWizardDidIt It's Magic!]] explanation, there are still rules to it, and Tedd creates a whole new field of study out of figuring out the laws and limitations of that magic.
** Elliot still ends up [[LampshadeHanging wondering how he still has his car keys]] after doing a series of costume-changing transformations (none of which have pockets).
*** Apparently, if he has anything in his pockets when he shapeshifts, it temporarily merges into Elliot. [[http://www.egscomics.com/index.php?id=2163 Such as his smartphone.]]
* Felucca's dragon form in ''Webcomic/{{Earthsong}}'' must be about 10 times her original size. Where does it all come from?
* Snookums the [[UglyCute Tentacle Bunny]] in ''Webcomic/TheInexplicableAdventuresOfBob'' was originally a {{Kaiju}}-sized giant monster, but he got [[IncredibleShrinkingMan shrunk]] to the size of a basketball and is now kept by Molly as a pet. He still retains all his original mass, though, so the earth shakes every time he hops around like a bunny rabbit.
* In ''Webcomic/{{Nodwick}}'' #4, the protagonist is forced to drink a magic potion of giant size to fool an invading army of orcs. As it turns out, the potion ''doesn't'' increase his mass, only his size, and his increased surface area leads him to be blown away by the ambient breeze.
--> '''Yeagar:''' Does anyone know why our '''fifty-foot henchman''' was just whisked into the sky by a '''thirty mile-an-hour breeze'''?\\
'''Artax:''' I might have an answer for you...\\
'''Artax:''' According to the fine print for "Plan #1", the growth potion increases '''volume''', but not '''mass'''.
* Averted in ''Webcomic/{{Drowtales}}'': Ariel uses whatever she has around to shapeshift into something bigger (such as creating {{wing|edHumanoid}}s), usually her hair and clothes but also a small dragon golem that was created with that ability in mind.
* Kieri from ''Webcomic/SlightlyDamned'' switches between being an angel and a snow bunny without much hassle. Considering her clothing pops in and out of existence as well, it's fairly safe to assume that it's guardian magic.
* Lampshaded in [[http://www.rhjunior.com/quentyn-quinn-space-ranger-0058/ this]] ''Webcomic/QuentynQuinnSpaceRanger'' comic.
* ''Webcomic/TalesOfTheQuestor'' specifically averts this with bogeymen. No matter what form they take, they retain their original (minuscule) strength and mass, to the point that a bogey taking on a really big form is essentially a cloud of blue gas. Played ruthlessly straight with [[http://www.rhjunior.com/tales-of-the-questor-0469/ spriggans]]...[[http://www.rhjunior.com/tales-of-the-questor-0470/ they hit really hard]].
* The Ambis in ''Webcomic/{{Jix}}'' all can [[OneWingedAngel transform into ugly beast versions of themselves]] and the more skilled can grow several times larger, such as Kelelder the Planet Thief, his daughter, and Maricax (a bounty hunter). It's never fully explained where the mass comes from or goes when they revert back to their normal size, though the creator hints at Animorphs explanation.
* ''Webcomic/TheNonAdventuresOfWonderella'': [[http://nonadventures.com/2012/09/22/my-cinnamons-exactly/ "My CINNAMONS Exactly"]] parodies this. Cinnaman, a shapeshifting villain made of cinnamon, can't transform into a larger horse because he doesn't possess enough mass. Wonderita asks why he doesn't just buy more cinnamon at the supermarket. Cut to Cinnaman, now 100 stories tall, rampaging through town.
-->'''Wonderella:''' [[NiceJobBreakingItHero Let's talk about what went wrong tonight]].
* An ''Webcomic/{{Oglaf}}'' monster can't violate conservation of mass, but people aren't fooled by a giant abandoned baby that's the size of 300 babies. So it [[spoiler:turns into a pile of 300 babies]].
* In ''Webcomic/PeterIsTheWolf'' weres gain some mass when they shift into beast form, but the actual amount varies from "runts" like Peter who only gain a couple inches of height (and several more inches [[GagPenis elsewhere]]), to Sarah who goes from five foot nothing and skinny to over eight feet tall and [[GagBoobs stacked]]. One character claims this is evidence that lycanthropy is supernatural (there's some debate in-universe).
* In ''Webcomic/AddictiveScience'' when a transformation changes someone's mass a "random" nearby person (usually Lukas or Mark) turns into something with an equivalent mass change.
* In ''Webcomic/SkinDeep'' some of the monsters are significant bigger in their natural form compared to their disguised human form. This relies on the magic of medallions, which (currently) no-one understands the workings of.
* Averted in ''Webcomic/LsEmpire'' with Snowball, who can multiply his size but can't change his mass. This results in a large --but ultimately very light-- penguin.
* ''Webcomic/TheOrderOfTheStick'' does a DeconstructiveParody - The mass a Hydra gathers from thin air to add to its new heads is turned into a source of free food once the monster is captured. And those villagers never went hungry again.
* In ''Webcomic/StarTrip'', the shapeshifting alien Khut is capable of changing their mass with their form, varying anywhere between a small animal a human can hold in their arms up to a form outclassing gigantic combat robots. It's noted that this should be physically impossible, as this is a science fiction comic where conservation of mass is normally in effect, but no one knows how Khut does it. [[spoiler: There's also Khudran, a self-aware fragment of Khut who generally takes even larger forms.]]
* In ''Webcomic/GirlGenius'', when Queen Alba shrinks down to (slightly over) normal human size too quickly, she overheats, suggesting she converts mass into energy. This doesn't explain where it comes from when she reverses the process, of course.
[[/folder]]

[[folder:Western Animation]]
* Jake from ''WesternAnimation/AdventureTime'' is an extreme example, being able to stretch to AttackOfThe50FootWhatever-scale on demand. One episode, "The Limit", explored what [[ExactlyWhatItSaysOnTheTin limit]] there is to Jake's shapeshifting, and he didn't reach it until he had stretched a ''great'' distance. But that was due to his organs no longer functioning, so the hypothetical limit of how massive he can become hasn't been explored yet.
* ''WesternAnimation/Ben10'' {{justifie|dTrope}}s this with the [[TransformationTrinket Omni/Ultimatrix]] being the source of all Ben's added and lost mass.
* ''WesternAnimation/CatDog'' isn't even a shapeshifter, but they can still stretch over miles and miles with no loss of volume when, normally, their body is just a few feet long.
* The ''WesternAnimation/ChipNDaleRescueRangers'' episode "Dale Beside Himself" features the Fleeblebroxians, a roughly mouse-sized alien race that can transform into anything with ease, for example a dragon the size of a small dog and several hundred times the mass of a chipmunk. This can hardly be explained by the fact that they consist of "unstable molecules".
* ''WesternAnimation/CostumeQuest'': The monsters use magic-powered human suits that ignore mass entirely. A brute-class monster immediately compresses and loses weight, while the kids and grubbins grow to fit the arms and legs.
-->'''Wren''': Nothing makes sense anymore.
* On ''WesternAnimation/TheFairlyOddParents'', every fairy suffers from this. Let's just say "AWizardDidIt" and move on. As these are the same fairies that regularly POOF! things into existence the baggage is one of the least JustForFun/{{egregious}} things about them.
* On ''WesternAnimation/{{Gargoyles}}'', sequences in which gargoyles awaken from "stone sleep" often show fragments of stone scattering from their skin as they re-animate, as if they're breaking out of a very thin coating of rock. Although there's plenty of magic in their Verse, "stone sleep" is described as a natural physiological quirk of their species, so losing an outer crust of stone every sunset ought to cost them whatever energy they'd allegedly accumulated from sunlight while immobile.
* {{Handwave}}d in ''WesternAnimation/GeneratorRex'' with nanobots. Not always a perfect solution there, though: nanites build stuff ''out of other stuff,'' so constantly generating his weaponry and vehicles, and doing it ''again'' when they get broken, means a lot of metal is being made from no apparent source; ''much'' more of it than Rex's body and nanites could possibly provide the material for. The plot of one of the episodes deals with another type of shapeshifter baggage: where do all the nanites Rex absorbs ''go''? It turns out that every now and then Rex has to go to a base in the Antarctic with giant, massive vats he has them drained into, otherwise the sheer quantity may make him go crazy.
** A quick moment in one episode had someone attempting to retrieve him from the ocean being dragged down carrying Rex until he retracted his giant metal fist, which raises so many questions then and there.
* Nobody's really sure where ''WesternAnimation/{{Kaeloo}}'' gets her extra mass when she [[HulkingOut transforms]]. Interestingly, Mr. Cat, the other shapeshifter in the cast, doesn't appear to experience significant changes in mass despite his wide variety of forms.
* Discussed in ''WesternAnimation/KipoAndTheAgeOfWonderbeasts'', where Kipo hysterically rants about her newly discovered half-Mute abilities. And this is ''before'' she discovers she can perform even more drastic limb shifting, such as turning her arm into a giant leopard leg:
-->'''Kipo''': I mean, my dad told me about "body changes", but [[PubertySuperpower nothing like this]]. I have fur that grows out of my arm, then goes away! [[LampshadeHanging WHERE DOES IT GO]]?
* In ''WesternAnimation/MyLittlePonyFriendshipIsMagic'', changelings, or at least Pharynx and Ocellus, can apparently transform into things much larger and heavier than themselves, with all the mass that the larger creatures would have. No explanation is given for the added mass.
* Imp from ''WesternAnimation/SheRaPrincessOfPower'' routinely took on forms that required an outside energy source to perform their function (and more energy than he could reasonably produce naturally) and he was never shown having to recoup what was lost. Notable examples are being a lit candle, two types of rocket complete with jet propulsion, flame thrower powerful enough to start a forest fire, and a laser rifle.
* Mostly averted in ''WesternAnimation/TheSpectacularSpiderMan''. Sandman loses some of his sand every time he fights, and has to be 'fed' raw silicate to keep the same mass. He only becomes bigger when he ingests ''more'' silicate, and becomes a giant after taking an entire beach's sand.
* Gems in ''WesternAnimation/StevenUniverse'' can shapeshift into just about anything with their HardLight bodies, but as Amethyst tells Steven when he tries to make himself taller, they can't keep their forms for too long or it'll make them worn out. As Steven is half-human, this ends up turning him into a baby until the following morning.
** In a later episode, when Amethyst has to impersonate Jasper, she soon starts sweating from having to hold a larger form for so long, and changes back as soon as the Rubies who were looking for Jasper aren't looking at her.
** Out of all the known Gems in the show, [[spoiler: Pink Diamond]] is the only one shown to easily shapeshift into a form much smaller than her without any complications, more specifically as [[spoiler: Rose Quartz]]. Possibly justified because [[spoiler: she was taller but significantly thinner as Pink Diamond, and so her mass as the shorter, fatter Rose was most likely similar - or maybe it's just Diamond mojo]].
* ''Challenge of the WesternAnimation/SuperFriends'' never explained where Apache Chief got the mass to grow 50 feet tall whenever he said "Inekchok!". People speculated that 500 cattle disappeared from the Great Plains whenever he did this. Clearly, this is ridiculous -- everyone knows that a Native American would absorb 500 ''buffalo'', not 500 cattle!
* In ''WesternAnimation/{{Teen Titans|2003}}'' Beast Boy has been everything from an amoeba to a Diplodocus, yet his base form couldn't weigh much more than 100 pounds. The same likely applies to his comic form. Beast Boy often uses this trope to his advantage. A typical move for him is getting up high with a small bird morph, then becoming an elephant or dinosaur to smash whatever's below him. Then there's his "patented wet-willy manouver", that is [[spoiler:he turned in a small bird, flew inside the ear of the gigantic Trigon and then turned into a ''whale'']]...
* ''WesternAnimation/XMenEvolution'''s Mystique, unlike her comics counterpart, is not limited by her mass, regularly transforming into a raven and flying away.
* Beast Boy uses similar physics-defying tactics in ''WesternAnimation/{{Young Justice|2010}}'' where he'll transform into a fast running or high jumping quick animal like a cheetah or monkey, get some serious speed or height, and then transform into a rhino or elephant to slam into them with all that extra weight moving at that momentum.
** In the ''[[WesternAnimation/YoungJusticeRevivalSeries Young Justice Season 3]]'' episode "Nightmare Monkeys", this is brought up by the Monkey God when he reveals the he had chosen Gar to receive his powers.
-->''"Why do you think you can only change into animals? And do the words 'conservation of mass' mean anything to you at all?"''
* In ''Franchise/{{Transformers}}'', extra mass is stored in pocket universes. Oddly enough, the parts of someone's alternate mode that don't really have anything to do in robot mode don't go away, and instead tend to form decorative "kibble". This technique is used mainly for changing size and storing weapons.
** The [[Film/{{Transformers}} 2007 movie]] specifically averted this by having the CGI computers track where every nut and bolt went during transformation. The result was that some robot forms were twice as tall as others. (The Allspark was the main exception; presumably being the Macguffin gives you the right.)
** The original cartoon did not explain where, for example, Optimus Prime's trailer went when he transformed from truck mode - it's just shown going out of shot or into the frame as required. (The trailer is supposed to turn into a battle platform, but frequently this was either ignored or forgotten.) This has become a long-running joke in the fandom, and even appeared in a ''WesternAnimation/TransformersAnimated'' short, where a kid asks Optimus where his trailer goes. As it turns out, Optimus doesn't know himself.
** There was, in fact, one episode of the G1 cartoon where, as Optimus transformed and his trailer started to move offscreen, it actually glowed briefly, then vanishes. Which becomes funny as in one incarnation, the trailer served as a holder (or whatever) for a pair of secondary robots. In the film series, it actually holds Optimus' spare guns. [[MoreDakka Lots and lots of spare guns]].
** In the IDW comics (the "-ation" miniseries at least) mass shifting, as befitting dimensional rupturing, required a ''lot'' of energy to do and [[PowerGlows generated quite spectacular fireworks]] due to laws of physics being broken. The headache was simultaneously decreased ''and'' increased by only having one character consistently mass-shift, but of course it was [[http://tfwiki.net/wiki/Size_changing Megatron turning into a gun.]]
[[/folder]]

[[folder:Anime and Manga]]
* Averted in ''Manga/{{Devilman}}''. When [[spoiler:Ryo's "father" died after being possessed by a demon, Ryo moves the corpse and discovers the weight is double what it should be]].
* ''[[Anime/{{Scryed}} s-CRY-ed]]'' is a good example of a justification of this trope, although transformation is only seen in one character and in a subset of the typical creation power. Whenever an Alter User summons their Alter, the mass they require for it is taken from surrounding objects or the environment itself. When protagonist Kazuma's Alter upgrades to the point where it's a true transformation rather than just a gauntlet, summoning it seems to involve breaking down his own regular arm to turn it into Shell Bullet, to say nothing of a few other uses of Alters that break down dead bodies, human or animal, for mass. Yikes. Taken up a further notch with another Alter User whose Alter is a HumongousMecha. His first use of it, in response to a bunch of villagers backing him to the edge of a cliff, was to vaporize ''them'' as material.
* In Kenichi Sonoda's ''Manga/CannonGodExaxxion'', the RobotGirl sidekick can shapeshift into a [[CoolBike hoverbike]]. She stores the excess mass needed to change in her breasts.
* ''Manga/FullmetalAlchemist'':
** Averted. Envy, despite [[NoBiologicalSex their]] lithe and feminine physique, is very heavy, and as a result, they make very deep footprints and can break a steel fence after a short fall, in addition to [[NoSell not even budging]] when Ed punches them in the face. This is noticed by the main characters and clues them in on the size of [[OneWingedAngel Envy's true form…]]
** [[Anime/FullmetalAlchemist The 2003 anime's]] version of Envy, meanwhile, only ever takes human forms within a certain size range and seems to weigh as much as a normal human. [[spoiler:The exception is the huge dragon thing in the climax, a form they shifted into once they passed through the Gates and got stuck in.]]
* Subverted in the lesser known manga ''Momoiro 1/10'' -- Momoiro is 50 feet tall and weighs several tons. When she's shrunken to the size of a normal human, she still weighs several tons and is denser than lead. Trying to walk across the top floor of her school causes the floor to collapse, running across a parking lot causes a trail of destroyed concrete, etc etc.
* The Franchise/{{Pokemon}} Ditto can change into 'mons of any size, but the [[Anime/PokemonTheSeries anime]] once subverted it with a Ditto that couldn't change size.
* In ''Manga/CaseClosed'', the APTX-4869 toxin has a million-to-one chance will [[FountainOfYouth de-age]] a victim back to when they're 8 years old. This is explained that it causes apoptosis to occur within non-neural cells, so that a large portion of tissue gets killed off and simply evaporates away. Shinichi described the sensation like his bones melting. However this doesn't explain how the re-aging antidote causes the mass to return.
* After the MagicPants, this is the second most common source of FridgeLogic in ''Manga/RanmaOneHalf'' whenever Jusenkyō transformations are concerned: Mousse, Shampoo, and Ryōga all change into smaller animals with no explanation as to where their mass goes, or where it comes from when they change back. Genma and Pantyhose Tarō change into larger animals (in Tarō's case, a chimera that is ''several'' stories tall). On a lesser scale, Ranma, Herb, and Rouge also lose or gain mass drastically, even if they remain roughly human-shaped (in Rouge's case) or merely [[GenderBender change sex]] (for Ranma and Herb). Might be justified in that [[TransformationRay Jusenkyō]] curses its victims with [[AWizardDidIt magical transformations]].
* ''Manga/{{Saikano}}'' uses this, but doesn't attempt to handwave it or anything of the sort.
* [[RidiculouslyHumanRobots Boomers]] in the ''Anime/BubblegumCrisis'' series present this problem. How can a man-sized android shaped like an ordinary salaryman sprout enough mass to turn into a HumongousMecha with [[CombatTentacles flailing tentacles]]? At least in one case it was because it was an absorbing type Boomer that used nanotechnology to fuse machinery, and eventually even scenery to its mass.
* The Invaders in ''Shin Manga/GetterRobo Armageddon''. For example, in one episode, the main characters respond to a distress signal from the ruins of New York City. When they get to the origin of the signal, they find two puppies and a dead person at a radio station, but the puppies afterwards turn out to be a pair of ''building-sized'' Invaders from a larger group that set a trap.
* The Saiyan ''Oozaru'' form from ''Manga/DragonBall'' is never fully explained; how does one quickly transform from a human-sized alien to a full-blown giant monkey? Of course, not much else makes "scientific" sense in that series. However, Oolong the pig's physical strength and body mass remain constant regardless of his current shape. Simply becoming a motorbike, for instance, doesn't guarantee he's strong enough for Bulma to ride.
** Likewise, Namekians regrow limbs and occasionally grow to the size of buildings, among other powers that make the Saiyans look plausible in comparison (for instance, Namekians don't need food - even plants in real life need nutrients from other sources in addition to air and water).
* Happens often in ''Manga/{{Naruto}}'', as it seems [[{{Mana}} chakra]] has NoConservationOfEnergy.
** [[spoiler:Orochimaru]]'s [[OneWingedAngel true form]] is revealed when he spits out a baseball-sized piece of something through his throat... which grows into a monster ''several times the size of his body''.
** Kimimaro can grow bones from his body and use them as weapons, apparently just by controlling the hormones of his body. Putting aside that [[RequiredSecondaryPowers he apparently needs to be able to survive removing his own bones without bleeding to death]] this would also require his body to have an infinite amount of calcium to make the bones out of.
*** The manga Kimimaro seems to have an accelerated healing factor which attempts to explain this, but really just invokes the "Biomass from thin air" part of this trope.
** While not exactly a shapeshifter himself, Shikamaru is able to change the shape of his shadow, and he is specifically limited by his shadow's current area.
* In ''Manga/{{Gantz}}'', the final boss of the Osaka mission "Nurarihyon" could change shape and size from a little old man to a monster the size of a high rise building, and is capable of splitting to multiple variable life forms of himself and demonstrates different powers with every different forms he assumes. He could survive being squashed to a puddle of blood and reform to another different gigantic monster instantly. [[spoiler:He was eventually killed off by consecutive blasts that squashed him to a blood puddle (again) by the main team leader, taking the bridge along with him.]]
** There was also a PuppeteerParasite which had the unique ability to clone and grow the body parts of its host, until they became a shambling BodyHorror of screaming heads, limbs, and even metal weapons. No explanation is given for their abilities or where the mass comes from, [[spoiler:only that they're one of many stowaway species accidentally collected by the Giants' ark ship.]]
* In ''Manga/AttackOnTitan'', [[spoiler:Titan Shifters are otherwise ordinary humans who]] can generate an entire Titan body out of thin air. It's implied that this is only possible because Titan flesh is about as dense as smoke, held together by their consciousness or something; Titans are noted to weigh a great deal less than something their size should, and dead Titans [[NoBodyLeftBehind rapidly evaporate]]. Despite this, Titans still exhibit many attributes that match the mass one would expect from something their size; they can crush buildings and fortifications by falling on or striking them, can be heard coming with thundering footsteps (and can leave deep footprints), and can pick up and wield massive objects.
* In the manga, ''Manga/{{NEEDLESS}}'', users of the Doppelganger Fragment (Mainly Eve Neuschwanstein) require large amounts of calories to shapeshift. Because of this, Eve drinks large amounts of a soda called Super Gel Dero Doro Drink that contains around 5,000 calories per can.
* In ''Manga/RosarioPlusVampire'', the bat narrator Kou-chan functions as the ShapeShifting weapon for Kokoa. The trope is subverted because Kou keeps his weight in any form, which is PlayedForLaughs on several occasions.
* ''Anime/Gundam00AwakeningOfTheTrailblazer'' actually averts this with the shapeshifting ELS: they are never shown turning into something larger or smaller than their original shape, and when they do want to form something larger, several of them combine themselves together into one mass to do it. They also are shown to take at least some time to seal a hole that gets blown in their bodies: they can't just regenerate the lost mass, they have to rearrange their structure to plug the hole.
* The [[ShapeshifterWeapon kagune]] of the titular creatures in ''Manga/TokyoGhoul''. Hand-waved as involving a specialized organic material called RC cells, it isn't clear how someone can store that much excess biological material inside their body without extra weight or mass. The most extreme example in the series has to be Eto, a 44-kg girl that routinely produces a {{Kaiju}}-type armor from her RC supply.
* Played with in ''Manga/MissKobayashisDragonMaid''. Dragons are capable of using magic to alter their size and (with enough skill) take on human form, with the excess mass being converted into {{mana}}. While this doesn't cause any weight problems, Tohru compares the feeling of all that compressed magic to wearing a suit that's several sizes too small.
* Played straight in ''Manga/UFOPrincessValkyrie''. Laine is incapable of modifying her height let alone her huge breasts. Because of the latter she is very bad at impersonating men. Her attempt at transforming into a small male dog goes as well as you'd expect.
[[/folder]]

[[folder:Video Games]]
* [[CuteBruiser Suika]] [[DrunkenMaster Ibuki]] from ''Franchise/TouhouProject'' has the power to manipulate the density of things. Among it's uses, she can [[AttackOfThe50FootWhatever grow to an enormous size]] with enough mass to perform {{Ground Pound}}s or turn into a mist (even into a [[OminousFog cloud of mist that enveloped the whole region]]). She can also split her mass into smaller sentient versions of herself, each with as much weight as can be expected of their size, but equal strength to the original.
** In her defense, in potential justification, she's a traditional [[{{Youkai}} oni]], allegedly responsible for performing impossible feats of strength and mysticism in Japanese lore. Further [[AllThereInTheManual supplemental material]] has her boast that she is a better magician than her fellow oni [[AmazonianBeauty Hoshiguma Yuugi]], who is outright stronger.
* The spirit channelers of the ''Franchise/AceAttorney'' series change their body shape and size to what the channeled spirit looked like when they were alive. Many mechanics of channeling, including the question where the extra mass comes from (or goes to) go unexplained in the series. Channeling is tantamount to [[AWizardDidIt magic]], mind you.
* Numerous cases in the ''Franchise/ResidentEvil'' series, where injecting oneself with any of the mutating serums tends to cause the subject to double in size and sprout all manner of tentacles and spikes. In ''VideoGame/ResidentEvil5'', [[spoiler:Irving]] goes from being about 5ft tall to twice the size of a blue whale in about 10 seconds. They truly outdid themselves with [[spoiler:Derek Simmons]] in ''Videogame/ResidentEvil6''. Not only does he grow into a massive T-Rex thing about the size of the average office building, but he ''freely transforms back and forth between this and his human form during the fight'' with absolutely no explanation of how it's possible. Even worse, one of his attacks is to shoot ''his own bones'' as ammo like an organic gatling gun. Good luck figuring that one out.
* ''{{Franchise/Metroid}}'':
** ''VideoGame/MetroidPrime3Corruption'': When fighting Gandrayda in Pirate Homeworld, she transforms into multiple characters you've already fought over the course of the game. Most of what she transforms into is sensibly around her own size, with the notable exceptions of a group of tiny Swarmbots (while they may collectively equal her size, she turns into multiple beings at once), Ghor and his ''ginormous'' powered-armor, and the massive Berserker Lord. Her scan page states that how she can change size so drastically is unknown.
** ''VideoGame/MetroidFusion'': X-Parasites tend to do this while mimicking creatures. Most creatures of roughly human to twice human size will require just one X, despite the X only being about the size of a basketball. Some other creatures, like certain SpacePirates, will require two or more ([[EliteMooks Golden Pirates]] have ''five'' for some reason) and bosses will generally have a larger Core-X surrounded by smaller X, showing at least a semblance of realism.
** Where exactly does Samus stuff her body when she goes Morph Ball? This is at least {{lampshade|Hanging}}d in ''VideoGame/MetroidPrime'', where one of the scans in the Phazon Mines reveals that the pirates attempted to copy morph ball technology, but... well, the results weren't pretty. If you peek in between the two halves of the Morph Ball in the ''Prime'' series it appears to be a case of Samus being converted into PureEnergy.
* ''VideoGame/{{Prototype}}'' averts this rather well. Size-wise all the people Mercer absorbs are about the same size as him. It's also strongly implied (though never stated) that Mercer weighs significantly more than a normal person does. [[GroundShatteringLanding Falling more than a few feet causes the pavement to buckle underneath him when he lands]] - falling great distances sends out a massive shockwave that can throw cars aside and kill bystanders!, which gives him plenty of mass for his larger powers (such as his Whipfist or Shield) or denser powers (Hammerfists, as in the page quote, and Armor).
** Also, whenever Alex uses his non-shapeshifting powers (like super-strength or clinging to walls), there's an effect that seems to imply mass is being expended. We see a similar effect when he's gliding. This seems to imply that he's "burning" the extra mass, keeping himself from getting too heavy.
** Try standing on a vehicle - most cars and other vehicles will be unable to move, and even ''tanks'' are slowed down by his weight. Using thermal vision, Alex is also far, far warmer than other humanoid entities (such as civilians, soldiers, etc.). Whether this is to make him easier to see and control for the player or yet more suggestion that he has much more mass is unknown. In thermal vision, Infected also appear brighter than normal civilians and even soldiers, which could imply that, like Alex, they are far denser than ordinary people.
** One has to wonder that if Alex has all that mass to create craters from very high falls and elbow drop with a heavy hammerfist to shatter armor among other things, how is it that he can flip (by tapping the jump button) onto a normal car (from the same level) and walk onto its roof and not have it crushed under what is supposed to be exceedingly heavy weight over a small area (a pair of feet)? After all, to throw an army truck without shoving himself in the opposite direction, he needs to possess a comparable amount of inertia himself, hence a cab-crushing amount of mass.
*** Unless of course he uses biomass to "adhesively" secure himself to the ground before throwing stuff that should still weigh a lot more than him. Doesn't really explain air-throws though.
** As long as he takes off his shield and armor, he can sprint as fast as a car and still trivially knock people down non-lethally... anyone?
*** Perhaps his armored shell prevents him from properly flexing and articulating his limbs as quickly as he can normally.
*** Even better: Ever tried shoving someone right next to a deformable object/terrain? What should been a shove that pushes someone moderately, if you miss, can dent cargo containers, vehicles, even a military base exterior fortification wall!
* ''VideoGame/ProjectEden'' has rats that transform into monsters over twenty times their original size, then turn into a small splash of green goo when they die.
* [[http://images1.wikia.nocookie.net/left4dead/images/6/6e/Tank-artwork.gif The Tank]] in ''VideoGame/Left4Dead''. According to the game, it takes place just a few weeks after the first infection. Yet, you regularly meet up with the thing pictured above.
** The same could be said for The Charger in ''VideoGame/Left4Dead2'', where his arm has become massive and covered with callouses.
** The Smoker, and to a lesser extent the Spitter, has somehow become ''much'' taller than an average human. The Smoker's tongue would also appear to be an example at first glance, but if you look closely enough you can see that they still have a normal tongue in their mouths and they're actually shooting something else out to grab survivors with (typically theorized to be intestine).
** The Boomer is an aversion, as their girth is all gas; their bodies have become swollen with noxious gas and bile that fills up in large boils across their body, which also means they only take about as much punishment as the regular, non-mutated infected before that gas causes them to pop like a balloon.
* In ''VideoGame/{{Halo 3}}'', the Flood has a pure form (which aren't based on an individual infected being) which can change its shape for various functions. Interestingly, the mobile form is quite small and light, but it can change into a large "tank" form in a few seconds which is significantly more massive, and its shooter form should be losing mass as it shoots, but it has no effect on its ability to change again.
* Averted in ''VideoGame/MegaManX'' with Axl; he has a copy chip that allows him to transform into any Reploid he has a genetic sample from, as long as said reploid is approximately the same size as him. However it's played straight with all the other new generation reploids (from which Axl is a prototype), some of which can [[spoiler:shapeshift into the 8 bosses, and Sigma]], all of whom are of different sizes. In ''VideoGame/MegaManX4'' it's safe to assume [[MeaningfulName Double]] keeps the extra mass in his huge gut needed to transform into his twice-as-tall combat form complete with Wolverine claws.
* ''VideoGame/BatmanArkhamSeries'':
** Anybody injected with the [[PsychoSerum TITAN drug]] in ''VideoGame/BatmanArkhamAsylum'' and ''VideoGame/BatmanArkhamCity'' grows to a huge size, ComicBook/TheIncredibleHulk-style. Where the extra mass comes from is never explained, nor is [[spoiler:where it goes when Titan!Joker came back to his original size]].
** Clayface in ''Arkham City'' is a gargantuan monstrosity, towering well above anybody in the game including TITAN henchmen and Bane. And yet [[spoiler:in the whole game he takes the form of the Joker, possibly the thinnest character in the game]]. He could theoretically be completely hollow inside, but then his [[ShapeshifterWeapon hammer-hands attacks]] would probably not hurt that much. Maybe he left most of his mass in the theater, while only going with a smaller body's worth to the steel mill. That's why the theater is boarded up - Clayface is still in there. Its also possible that he is extremely dense and used his acting and shape shifting abilities during [[spoiler:the fight with Clayface!Joker just before Protocol 10]] to fool Batman.
* Averted in a plot-significant manner in ''VideoGame/{{Flashback}}'': The game revolves around shapeshifting aliens infiltrating humanity. The tell? They're ''extremely dense'' as a side effect of having enough mass to shift to larger forms -- the protagonist first discovers them with the aid of glasses that can analyze molecular structure and determine an object's density at a distance... and suddenly discovers people that have a far higher density than seems to make sense.
* ''VideoGame/TheThing2002'': [[spoiler:Whitley]] goes from an ordinary Man-Thing to a ten story high monster when he finally transforms for the FinalBoss fight.
* In ''VideoGame/NetHack'' regeneration is handled realistically - while under any sort of rapid regeneration effect (either granted magically or naturally), your hunger meter will drain 50% faster than normal. Polymorphing however, is not - you can polymorph into anything from a tiny bat to a gigantic dragon with no explanation for where the extra mass comes from or goes. Some monsters will do this regularly, such as wererats which rapidly shift between human and rat forms, or chameleons, whose natural form is the same size as a real life chameleon but who can change into any other creature in the game.
* ''VideoGame/WorldOfWarcraft'''s druids can shapeshift into a cat, a deer, a bear, a bird, a seal, an owlbear, and a treant. No mention is ever made of how this is actually possible. It's not that they make their mass less dense, since the bird can actually fly and the deer can carry a rider. How it is physically possible for a 9 foot Tauren to become a cat boggles the mind... much less how a warmblooded mammal becomes a treant. Especially since shapeshifting doesn't even cost mana. The game's magic usually makes some degree of sense, even if it violates the real world's laws of physics (often it-at least canonically-obeys the law of conservation of energy, for example). This though, makes no sense at all.
** There is also the polymorph spell, which can temporarily turn anyone into a sheep (or pig, or frog). Player characters range in size between 4ft and 9ft, and polymorph can also be used on a warlock's demon pets (who can but up to 12ft in height). Again, no explanation is offered for how this works.
** There are also the dragons, who can take the forms of humanoids as they wish. Dragons are enormous creatures, but they start out tiny. Tiny whelps can take the shape of a human child, and collossal adults can take the form of a human. There's a 2ft difference between a human child and a human adult, while there's a 6ft difference between a whelp and an adult. How this works is anybody's guess. It's not an illusion, since a dragon who encounters itself via time travel shenanigans can't shapeshift.
* ''VideoGame/Prey2017'': Typhon Mimics, despite being no larger than a dog, can perfectly imitate anything from a pen to a shipping crate. You can find an email chain in-game from a group of scientists trying to figure out how it works, with theories including a 'fake' shapeshift using directed hallucinations, swapping places with the desired object in an alternate dimension, and, in frustration after many inconsistencies are pointed out with the others, '[[AWizardDidIt magic]]'.
[[/folder]]

[[folder:Literature]]
* Originally in ''Literature/{{Animorphs}}'', the size/mass changing was essentially {{handwave}}d by explaining that a character's [[LegoGenetics DNA is "rebooted"]] every time they transform. But in a later book, Ax explains that morpher's extra mass is stored in a pocket universe when s/he is in a smaller form, or taken from there when in a larger form... which also happens to be the hyperspace bypass that starships use. He even points out that the extra mass has to go ''somewhere''. There's a MillionToOneChance of having one's stored extra body mass run over by a random spaceship. Needless to say, the Animorphs are less than thrilled with this info. This actually happens in one book, whereupon the main characters (who were mosquitoes at the time) connected to that mass are "slingshotted" onto the ship... and take several minutes to put themselves back into one piece. With [[BodyHorror disgusting results for the onlookers]]. (The Animorphs aren't too interested in hearing about how they rewrote the Andalite science textbooks.) But though we learned where the extra mass goes with ''smaller'' morphs, just where the extra tonnage comes from when you go from teen to T-Rex remains a mystery.
** Played straight, however, with the Helmacron "shrink ray". Animorphs and Yeerks are shrunken and unshrunken with impunity, without even a HandWave as explanation.
*** The Shrink ray technology came from manipulating the morphing cube that gave the kids their powers. So presumably the Helmacrons used the same pocket dimension mass swapping technology just for a permanent shrinking effect instead of a temporary morphing one.
* In Brandon Mull's series "Beyonders", there is a shapeshifter with a limited amount of mass. To kill it, one must cut pieces off until it becomes small enough to be ignored. The shapeshifter mentions it uses copious amounts of internal body armor if it needs to disguise its mass.
* ''Literature/BooksOfTheRaksura'': The titular {{Draconic Humanoid}}s can [[{{Humanshifting}} shift into a normal human form]], whatever their original size; the extra mass is assumed to go wherever their human clothes go when they shift back. Stone, who's been [[StrongerWithAge growing for centuries]], has to jump off an airship deck before shifting so the mass of his 60-yard wingspan doesn't founder it.
* In Vicki Ann Heydron's short story "Cat Tale", a woman's idle wish to know what it's like to be a cat is granted; while she was thinking of a housecat, she's amused to realize that conservation of mass has made her a mountain cat.
* Katherine Kerr's ''Literature/{{Deverry}}'' series, despite being magic based, required Dweomer workers who change shape to retain their mass. Making them quite large birds.
* This is averted in some ''Literature/{{Discworld}}'' books, being first mentioned as early as ''Literature/EqualRites'' when Esk doubts that Granny Weatherwax can turn into animals because "If she turned herself into a fox what would happen to all the bits that wouldn’t fit?" Similarly, in ''Literature/TheWeeFreeMen'', a character who has been transformed into a toad wonders, "what happened to the rest of me?" In [[Literature/AHatFullOfSky the next Tiffany book]], we learn exactly what happens and [[BodyHorror it ain't pretty]]. [[spoiler:If a witch turns someone into a frog, they actually turn them into a frog and a large amorphous free-floating blob of chemicals.]] In other books this doesn't happen, though. Essentially the Shapeshifter Baggage question raises a conflict between two fundamental Discworld laws: the Law of NarrativeCausality (which says it should work like it does in stories) and the Law of [[EquivalentExchange Conservation of Reality]] (which says it can't be that simple). It's also possible that it depends on ''how'' the shapeshifting occurs; "natural" shapeshifting and ForcedTransformation via mental tricks and morphic fields have "neater" results than using magic to directly warp someone's shape. In addition, the witch who had to deal with the baggage had a lot of raw power but no relevant training, while the cleaner ones are done by some of the most powerful wizards in the world or by the use of Fairy Godmother wands (which are mysterious artifacts that bypass or ignore all the usual magic rules).
** Like most things in Discworld, RuleOfFunny takes precedence, followed by RuleOfCool. Greebo the cat is a large cat, as cats go, but his human version is specifically described as being six feet tall and muscular, because the plot clearly requires it.
** Vampires don't have to follow mass conservation rules, but they find it easier to turn into many bats rather than a single bat, especially if they've been off human blood for a while. And because the ''Literature/{{Discworld}}'''s GenreSavvy universe understands what FanService means, male vampires can shapeshift with their clothing, while female vampires can't.
** It isn't stated that Angua is a similar mass in either form but the differential isn't huge -- about 25% -- so a short human woman would weigh about 50kg and a male wolf up to 45kg.
* Featured regularly in Creator/JimButcher's ''Literature/TheDresdenFiles''. Conservation of mass isn't a problem at all for magical shapeshifting thanks to ectoplasm. When a creature shapeshifts, or when something from the Nevernever (faerieland) comes to the real world, the matter (in the case of a shapeshifter, the extra mass layered over their real body; in case of a demon, their whole physical body in the real world) is formed out of ectoplasm from another dimension, animated and given substance by magic. When that magic is withdrawn, the ectoplasm turns into an equal mass of a inert, clear, viscous goop which is an inconvenient mess but quickly evaporates. Arguably justified, in that there's an explanation of and consistent rules for where extra mass comes from that make as much sense as anything else in the series: leftover ectoplasm has been used to identify a crime scene as magical in nature, and I'm sure that characters have slipped and fallen on the stuff at some point or other.
** This doesn't seem to explain how shapeshifting into something smaller works, though. Where does the extra mass go? The Nevernever? If so, how is it protected from some nasty spider-goblin thing that probably wants to eat it?
*** According to the official RPG, that's exactly what happens. It's presumably sent to something like a Demesne: a small pocket of the Nevernever under the way of a specific being, which is generally hard to reach unintentionally, as well as uninhabited by anything else. The [[DirectLineToTheAuthor margin notes from Harry and friends]] specifically mention this as a good adventure hook.
* In ''Literature/ExpirationDate'', a fugitive ghost is briefly able to disguise the body it's inhabiting by adding biomass to increase the body's height and shape. The question of where the extra biomass comes from is addressed, and it's not pleasant: [[spoiler:it's taken from the dog that was hunting them, which does not survive the process]].
* In the [[Literature/FafhrdAndTheGrayMouser Fafhrd and Gray Mouser]] novel ''The Swords of Lankhmar'' by Creator/FritzLeiber, a shrinking potion does, in fact, displace mass, as the now rat-sized Mouser has to swim his way out of a good-sized puddle of meat, cloth fibers, and metal fragments (flesh, clothes, armor, and weapons). Later, he grows back to his full size away from that puddle, and the mass is taken from nearby objects (and people!), notably a very fat girl who finds herself suddenly slim. Great news for her, {{Squick}} for Mouser?
* ''Literature/GarrettPI'': In ''Petty Pewter Gods'', the flying horses' torsos slim down drastically when their wings sprout via shapechanging, and plump up again when they retract them after landing.
* {{Handwave}}d in ''Literature/TheHalfBloodChronicles'', by Creator/MercedesLackey and Creator/AndreNorton. Dragons shapeshifting to a smaller form have to shunt their extra mass into an extraplanar space they call [[{{Hammerspace}} the Out]]. A dragon in human form, when viewed in the magical spectrum, can be seen as a human surrounded by a dragony "shadow". This shunting also takes a certain level of skill on the dragon's part. Taking a form that's the same size as the dragon in question is simple. Taking a form as small as a human or elf is a challenge.
* In the ''Literature/IronDruidChronicles'', this is handwaved. Magic disobeys the laws of physics all the time. It works however [[ClapYourHandsIfYouBelieve people believe it works]]. And since widespread knowledge of the laws of physics is a fairly new thing... yeah. All of the "Old Ways" disregard the laws of physics, such as a druid's shape shifting, or Coyote's resurrection.
* In the ''Literature/JaneYellowrock'' series, by Faith Hunter, Jane is a SkinWalker, capable of copying the genetic code of animals and possibly people to assume a new form. This Native American magic allows her to sloth off mass and store it 'else-where' (mainly stones and sand) and to gain mass to grow in size. Interestingly enough Jane likes to only absorb or deposits mass into stone because to her it doesn't have any individual traits aside from being empty matter.
* Explicitly averted in the Literature/KittyNorville novels. The easiest way to distinguish a werewolf in lupine form from its mundane counterpart is the fact that they are normally ''at least'' half again as large as the 36 kg (80 lbs) norm.
* Dragons from ''Literature/KronikiDrugiegoKregu'' need a "pattern" for the specific organism to shapeshift into, as well as ''loads'' of additional energy -- [[BigEater huge amounts of meat]], in other words. Or soil. Or at least apples, though carnivorous dragons think these are yucky.
* In ''Literature/Liar2009'' by Justine Larbalestier this is explicitly averted; werewolves are exactly the same mass in both forms.
* In ''Literature/LoyalEnemies'', there's no explanation given for where the dragon Gloom's mass goes when he changes forms between dragon and human, despite being horse-sized as a dragon and an average human in size, respectively.
* Creator/StevenErikson's ''Literature/MalazanBookOfTheFallen'' has this feature for both Soletaken and D'ivers (single- and multiform shapeshifters, respectively). Depending on which one of these beings you encounter, you might be up against a grown man who can become a hawk and fly away... Or something that can become one or more dragons. At least the undead shapeshifter can't become living...
* In Creator/FrankHerbert's novel ''Man of Two Worlds'', a shapeshifting alien is captured by humans and is confined to a cell with only a small drain being the way out. He laments the fact that he can't simply destroy his own mass so that he can become small enough to fit through the drain. Too late does he realize that he could have just turned into a snake and slithered down the drain, without having to bypass the law of conservation of mass/energy.
* The kandra of ''Literature/MistbornTheOriginalTrilogy'' explicitly ''are'' bound by Conservation Of Mass. This comes up a couple of times in the third book, including one where the hero takes advantage of the fact that the same body mass that makes for a scrawny human makes a fairly beefy wolfhound and one where the same hero quickly shifts up from dog to horse by eating an entire pig for the extra mass. Normally, however, this isn't a problem for them, as they have to digest their target to produce an exact imitation, which, by definition, gives them enough mass to transform.
* Goes all over the place in the ''Literature/MercyThompson'' series. Werewolves always gain mass when they transform: a woman who's 120 pounds as a human will be more like 180 pounds as a werewolf. Adam, who's a pretty big guy when he's human, becomes an enormous werewolf. Mercy, on the other hand, is a mere thirty pounds as a coyote. She also admits to being totally baffled by how [[TheFairFolk fae]] glamours work, as they're not exactly shapeshifting yet can still, in her words, "somehow allow a nine foot tall ogre to fit into a size four dress."
* Averted in Creator/PoulAnderson's ''Literature/OperationChaos'' where all animal based lycanthropes must observe Conservation of Mass. The 180 pound hero transforms into an 180 pound wolf, while a Giant Mook who turns into a tiger is "seven feet tall and monstrously fat."
* Kelley Armstrong's werewolves in her ''Literature/TheOtherworld'' series retain the same mass in either form, and have to eat lots to account for their higher metabolism.
* In the ''Literature/PerryRhodan'' universe, shapeshifters with actual physical bodies of their own that they depend on generally do have to obey conservation of mass no matter how flexible they may be otherwise; the same is not necessarily true of EnergyBeings taking on a physical form for their convenience, however, and given the number of handwaves involved in psi and hyperspace physics the line between the two can get a bit blurred on occasion (as it arguably does with e.g. the Cynos, who do seem to combine traits of both).
* Averted in Creator/DeanKoontz's novel ''Literature/{{Phantoms}}''. The BigBad monster can change its shape and detach pieces of itself, but it must obey conservation of mass. Its creations often appear outsized when it tries to imitate something too small or too be big, and it's only able to imitate a much smaller creature by splitting itself apart.
* ''Literature/{{Safehold}}'': Merlin can change his appearance, but his mass and rough body dimensions always remain the same. The fact that all the ''seijins'' who are popping up are the exact same height and are never visibly active at the same time allows [[spoiler:Aivah]] to figure out that they're all the same person.
* Averted in ''Literature/SectorGeneral'', where Dr. Danalta does not, in fact, lose or gain any mass when it changes shapes... so when it turns into something that looks like a teddy bear, it is still a very heavy teddy bear.
* Used and {{lampshade|Hanging}}d in ''Literature/TheShapeshifter'' book series, Dax Jones can turn into a fox, but has no idea where his clothes and whatever he is carrying disappear to when he does.
* ''Franchise/StarWarsLegends'':
** In the ''Literature/GalaxyOfFear'' series, the race known as the Shi'ido can shape-shift. It's explained that due to their extremely long lifespan, in which they can live for 500 years and only people older than 61 are considered adults (makes you wonder what their drinking age is), their shapeshifting ability improves with age. Young Shi'ido can only change skin color, older ones could change into any humanoid species they wanted, and ones even older can change into whatever. However, if they tried to change beyond their natural boundaries, they'd be [[ShapeshifterModeLock stuck in that form for weeks or months]]. How exactly they could change isn't well explained, but ''The Essential Guide to Alien Species'' said something to the effect that they have folds of extra skin under their skin that they can use if they need to to change into larger or smaller species (or rocks and trees, apparently). Also, since some species identify others with smell as well as sight, and the Shi'ido aren't perfect at what they do, it's explained that they use telepathy to get around (what could be described as) LatexPerfection.
** ''Galaxy of Fear'' has Hoole ignore conservation of mass whenever he needs to. If he's escaping with the child protagonists on a skimboard that won't take his extra weight, he can just turn into a small rodent that doesn't burden the craft. He once becomes a mammoth frog to carry them one at a time over a wall, and he can be a small flying animal to cover ground quickly. The times when he ''can't'' turn into something that gets him out of whatever situations he's in, so that it's the ingenuity of the kids that saves the day, sometimes seem arbitrary.
** Clawdites, the species of the female bounty hunter in ''Attack of the Clones''. For them to transform it requires great concentration, which was broken slightly during the speeder chase with Anakin, and they are incapable of changing mass significantly. The [[TabletopGame/StarWarsRoleplayingGame RPG expansion]] that introduces Clawdites as a playable race notes that their shapeshifting ability is fluid-based, and that some individuals use a specially-built saline pump on their person to increase or decrease their mass. Even then, however, growing or shrinking beyond the size of an average humanoid is out of the question.
* ''Literature/TheStormlightArchive'': The singers are capable of shifting between forms by bonding any of several spren, and these forms can have notably different sizes and builds. For example, a singer can shift between dullform (a little shorter than the average human, and not incredibly bulky) to warform (at least a foot taller, and a lot more heavily muscled), with no explanation given as to where the extra biomass comes from. Or where it goes if he shifts from warform back down to dullform, for that matter.
* Tofu from ''Literature/SuperMinion'' does obey conservation of mass, and on top of that he also needs a lot food to [[CastFromCalories power his shapeshifting]]. His solution is to use ultra-dense muscles so that he can weigh over three hundred pounds while still looking like an unremarkable 18-year-old. For a while, his obsession with stockpiling energy gets so bad that it actually starts to slow him down.
* The ''Timeweb'' trilogy by Brian Herbert takes the more obvious approach: shapeshifters grow larger by absorbing rocks and dirt into their own mass. Growing smaller is somewhat like shedding snakeskin, and can be a bit disgusting if a massive change is needed.
* In Creator/SheriSTepper's ''Literature/TheTrueGame'' series, shapeshifters can increase their mass by incorporating additional organic material (Mavin uses a sack of grain at one point); when they decrease their mass the excess is expelled, resulting in what looks very like a pile of minced beef.
* In ''Literature/VoidCity'', vampires have the power to shapeshift into one or more animals, but how it works varies between individuals. Some are able to take their clothes with them, while others have to leave their clothes behind. Eric actually generates new clothing: even if he starts out naked, he'll be in his usual casual clothes when he changes back. As a result, he's accumulated tons of identical outfits. Everyone just accepts it as a natural part and parcel of a vampire's magic powers.
* Creator/HarryTurtledove not only keeps to the principle (illustrated distinctly by a couple werehawks too heavy to fly) in ''Literature/{{Werenight}}'', he gives Poul Anderson's Giant Mook a semi-affectionate nod... and upgrade. An "immensely tall, immensely fat" barbarian chief turns into a '''sabretooth'''. A ''big'' sabretooth.
* Averted in the ''Literature/WildCards'' series, where Kid Dinosaur can change shape into any kind of dinosaur, but explicitly does not change mass. This results in such things as a 3 foot tall T-Rex.
** Played straight with another character who's body stored everything he ate (he never had to go to the bathroom) and kept absorbing until he had enough mass and excess food to go into a prolonged hibernation, during which his body would radically change (as would his powers).
** Skewed with Rahda "Elephant Girl" O'Reilly, who is a Irish-Hindu were-elephant. Her excuse is that she absorbs energy from the environment and converts it into mass; this can black out a city if used in the right location. Likewise, when she changes back the excess mass converts into a flash of light. Of course, the amount of energy needed to convert into a couple of tons of elephant flesh is incredibly titanic; and the energy release from changing back should wipe out a continent. So it's neither averted nor played straight.
* The novelization of the 2010 ''[[Film/TheWolfman2010 Wolfman]]'' movie makes note of the extra mass Lawrence gains when transforming into a werewolf, and suggests its source is hell itself.
* In ''LightNovel/IsItWrongToTryToPickUpGirlsInADungeon'', Lili's transformation magic, Cinder Ella, is limited to people around the same size as her. As a result, she can only transform into small humans, dwarves, chientropes, and other pallums.
* Addressed in ''Literature/TheMagicians'' when the students learn VoluntaryShapeshifting; the biggest hurdle for mastering the process of transforming from a human into a goose is in learning how to correctly shed the body mass and magically store it away, then reapplying it during the return to human form.
[[/folder]]

* In ''Manga/RosarioPlusVampire'', the bat narrator Kou-chan functions as the ShapeShifting WeaponOfChoice for Kokoa. The trope is subverted because Kou keeps his weight in any form, which is PlayedForLaughs on several occasions.

** [[Wiki/{{Wikipedia}} The Other Wiki's]] article on the Hulk states that gamma rays, being the most powerful form of energy known, are so strong they can actually transform energy into physical mass, possibly explaining the increase in size. Now, as for where the mass goes when he transforms back, that's anyone's guess.

* This is averted in some ''Literature/{{Discworld}}'' books, being first mentioned as early as ''Literature/EqualRites'' when Esk doubts that Granny Weatherwax can turn into animals because "If she turned herself into a fox what would happen to all the bits that wouldn’t fit?" Similarly, in ''Literature/TheWeeFreeMen'', a character who has been transformed into a toad wonders, "what happened to the rest of me?" In [[Literature/AHatFullOfSky the next Tiffany book]], we learn exactly what happens and [[BodyHorror it ain't pretty]]. [[spoiler:If a witch turns someone into a frog, they actually turn them into a frog and a large amorphous free-floating blob of chemicals.]] In other books this doesn't happen, though. Essentially the Shapeshifter Baggage question raises a conflict between two fundamental Discworld laws: the Law of NarrativeCausality (which says it should work like it does in stories) and the Law of [[EquivalentExchange Conservation of Reality]] (which says it can't be that simple). It's also possible that it depends on ''how'' the shapeshifting occurs; "natural" shapeshifting and BalefulPolymorph via mental tricks and morphic fields have "neater" results than using magic to directly warp someone's shape. In addition, the witch who had to deal with the baggage had a lot of raw power but no relevant training, while the cleaner ones are done by some of the most powerful wizards in the world or by the use of Fairy Godmother wands (which are mysterious artifacts that bypass or ignore all the usual magic rules).

* In ''TabletopGame/DungeonsAndDragons'', the various VoluntaryShapeshifting and BalefulPolymorph spells and abilities ignore conservation of mass, as demonstrated by 125-ton dragons {{Humanshifting}} into standard-size humanoids. Some editions explain this as magic drawing energy and material from the [[ElementsOfNature elemental Planes]] to fuel their effects.

** In a later episode there is an attempt to avert this by having Odo leave some mass behind in a puddle on the Promenade when transforming into a bird. This... [[VoodooShark only creates new problems.]]

** When fighting Gandrayda in ''VideoGame/MetroidPrime3Corruption'', she transforms into multiple characters you've already fought over the course of the game. Most of what she transforms into is sensibly around her own size, with the notable exceptions of a group of tiny Swarmbots (while they may collectively equal her size, she turns into multiple beings at once), Ghor and his ''ginormous'' powered-armor, and the massive Berserker Lord. Her scan page states that how she can change size so drastically is unknown.
** X-Parasites also tend to do this while mimicking creatures. Most creatures of roughly human to twice human size will require just one X, despite the X only being about the size of a basketball. Some other creatures, like certain SpacePirates, will require two or more ([[EliteMooks Golden Pirates]] have ''five'' for some reason) and bosses will generally have a larger Core-X surrounded by smaller X, showing at least a semblance of realism.

* ''Anime/Gundam00AWakeningOfTheTrailblazer'' actually averts this with the shapeshifting ELS: they are never shown turning into something larger or smaller than their original shape, and when they do want to form something larger, several of them combine themselves together into one mass to do it. They also are shown to take at least some time to seal a hole that gets blown in their bodies: they can't just regenerate the lost mass, they have to rearrange their structure to plug the hole.

* Averted in ''Manga/{{Devilman}}''. When [[spoiler:Ryo's "father" died after being possessed by a demon, Ryo moves the corpse and discovers the weight is double what it should be.]]

* ''[[ComicBook/TheIncredibleHulk The Hulk]]''.

* In ''ComicBook/{{Supergirl}}'' storyline ''ComicBook/TheKillersOfKrypton'', it is not explained how Empress Gandelo can grow to gigantic size, or where her extra mass goes when she goes back to her normal size.

* Creator/JohnCarpenter's ''Film/{{The Thing|1982}}'' is ''mostly'' fairly good with this, with The Thing usually seeming to obey conservation of mass. However, at the end the [[spoiler:Blair Thing]] is able to turn into a quite large monster. In fairness, he is shown attacking another man first, and it's ''possible'' he consumed additional material since the transformation happened offscreen (another character who vanishes during the climax was supposed to have been assimilated as well, but the scene was cut to avoid SpecialEffectsFailure).

* In the spoof film, "Film/EpicMovie", a parody of Mystique played by Creator/CarmenElectra drags the character Peter into a tent to have sex with him. After making out with him, she asks him what he wants her to shapeshift into. He at first asks for [[BreastExpansion bigger boobs]] and a big booty. He then asks for a monobrow, [[ChubbyChaser "Big Flabby Grandma Arms", and "Bingo Wings, like a fat blue Britney Spears."]] She ends up changing into an entirely different, fatter actor. It's never explained how she can change size.

* An ''Webcomic/{{Oglaf}}'' monster can't violate conservation of mass, but people aren't fooled by a giant abandoned baby that's the size of 300 babies. So it [[spoiler:turns into a pile of 300 babies.]]

* Beast Boy uses similar physics-defying tactics in ''WesternAnimation/YoungJustice'' where he'll transform into a fast running or high jumping quick animal like a cheetah or monkey, get some serious speed or height, and then transform into a rhino or elephant to slam into them with all that extra weight moving at that momentum.

* Played with in ''Manga/MissKobayashisDragonMaid''. Dragons are capable of using magic to alter their size and (with enough skill) take on human form, with the excess mass being converted into {{mana}}. While this doesn't cause any weight problems, Tohru compares the feeling of all that compressed magic with wearing a suit that's several sizes too small.

* ''Film/TheIncredibleHulk'': Where does all that sudden biomass come from? And where does it go? In the first ''Film/{{Hulk}}'' movie (not the one with Norton), every time Banner is seen returning to human form, we see steam emanating from him and water dripping from every pore of his body, slicking his hair to his head and soaking the MagicPants to him. The suggestion seems to be that the excess mass is created by rapid cell division and when he calms down, the cells are turned into steam/water and are shed thusly. It wouldn't be the strangest thing to happen in a Marvel movie, but cell division does not actually ''create'' mass.\\\

*** [[FridgeHorror A gamma ray burst?]]

* Slightly (and disgustingly) avoided by Big Bertha of the [[Comicbook/GreatLakesAvengers Great Lakes... um, at the moment, Initiative]]. It's not explained where the extra mass comes from when going from supermodel Ashley Crawford into I-stop-traffic-the-hard-way Big Bertha. But after the heroics are done, she does have to expel the extra mass... by ''vomiting'' it back out. She doesn't like it any more than you do.

* Averted by Franchise/TheDCU's Comicbook/MartianManhunter. In an issue of his solo series, he reveals that he can borrow mass from the Earth. He also dodges it in that, since he can make any part of himself intangible and invisible, he can hide any excess mass he's not using.

* ''ComicBook/TheTransformers'' is explained in greater depth down the page in Animation, but the comics have the same issues with Megatron transforming into a gun and Soundwave and Blaster as cassette players, all about big enough to fit in their hands in robot mode. A more noticeable example is Broadside, a triple-changer with alt-modes as both an aircraft and an aircraft carrier.

* He uses similar physics-defying tactics in ''WesternAnimation/YoungJustice'' where he'll transform into a fast running or high jumping quick animal like a cheetah or monkey, get some serious speed or height, and then transform into a rhino or elephant to slam into them with all that extra weight moving at that momentum.