In fiction, shapeshifting is a varied, complicated business. Some especially fortunate metamorphs have the ability to transform into just about anything, taking on the necessary shape through imagination alone. Other shapeshifters don't have it so easy, and in order for them to gain a particular form, they actually have to go to a certain degree of effort.
Shapeshifters with this limitation often need some form of contact with the person or creature they're mimicking: in the simplest variant of the trope, they need to get a good look at the potential form up close; more complicated variants require the shapeshifter to get a sampling of DNA in order to properly replicate their form, sometimes through violent or even lethal means; in extreme cases, they may even need to study the target at length just so they can understand the intricacies of their newest disguise... in which case, the form hopefully remains with them permanently once it's fully assimilated. From time to time, even weirder processes may be utilized.
In some cases, this business is just a chore that the shapeshifter has to perform in order to get to the good stuff, but others may regard the act of gathering new shapes as a hobby, or maybe even their mission in life. Additionally collecting more forms can mean that the Shape Dies, Shifter Survives, leaving the shapeshifter with more options to burn through before they really need to worry about death.
See also Face Stealer and also You Are Who You Eat, the extreme variations of this trope. Can overlap with Kill and Replace, especially if the doppelganger needs to kill their victim in order to copy their form. See also Transferred Transformation and Physical Attribute Swap.
- My Hero Academia: Himiko Toga has to consume the blood of her targets in order to shapeshift into them. She collects vials of their blood, which allows her to use their form for as long as she has any blood in the vials left to use.
- One Piece: Mr.2 Bon Clay, real name Bentham, ate the Mane Mane no Mi (Clone-Clone fruit), allowing him to mimic anyone's physical form provided he's touched their faces. In addition to him, the Wano Country Arc reveals that a previous user of the fruit helped Orochi usurp the Kozuki clan to become Shogun.
- That Time I Got Reincarnated as a Slime: Rimuru's Predator skill allows him to duplicate the forms of creatures he absorbs, along with their abilities, with his default human form resembling Shizue Izawa. Additionally, he can create fusions of aspects of these forms simultaneously, such as when he creates his Doppelgänger when fighting Hinata Sakaguchi
- Cubix: Robots for Everyone: Kilobot can absorb data from other robots, allowing him to mimic their appearances, voices, and powers.
- 52: Everyman is a shapeshifter who can only assume a form if he's eaten a small piece of it first. When this is brought up, his teammates note that he's turned into such things as a gorilla or a giant crab...
- Legion of Super-Heroes: Chameleon Boy can copy new forms by scanning them with his antennae (though he is also shown to be able to create new forms through sheer imagination).
- Teen Titans: Beast Boy can shift into any animal form he knows of, including extinct animals (like dinosaurs) or alien animals. But he has to get a good look at it, and he always turns out green.
- Wolverine: The villain Dirtnap is a mutant shapeshifter who has to "absorb" someone before he can shapeshift into their likeness. Trying to absorb Logan didn't work, as Logan's healing factor easily outpaced the absorption process, and Dirtnap had to retreat.
- Inception: Eames can shapeshift in dreams; however, he indicates that he needs to examine a target closely first before he can accurately assume their form. When preparing for the mission, he sneaks himself into the offices of Fischer Morrow in order to study Christopher Browning up close and learn his mannerisms so he can later pose as him. Because this ability is dependent on memory and acting ability, Eames can't impersonate projections sent after the team, but he does have a few shapes he can recall from past jobs, allowing him to become "a lovely young lady I've used before" while stealing Fischer's wallet in the second level.
- Terminator 2: Judgment Day: The T-1000 can shape its limbs into simple weapons without any kind of study, but in order to disguise itself as other organisms or inanimate objects, it needs to sample the target through physical contact first. In one case, it mimics a stretch of floor, then waits for a security guard to step on it so it can assume his form — and then kills the guard for good measure. In the finale, getting frozen with liquid nitrogen and thawed out causes T-1000 to malfunction, resulting in it imitating anything it touches regardless of whether it wants to or not.
- In The Forest of Dreams by Nathan Page, a fan-written entry in the Fighting Fantasy gamebook series, the protagonist belongs to the race of Shape Changers who can assume the shape of any creature — but to do this, they have to collect the creature's life essence, which can only be done at the moment when the creature is dying.
- Animorphs: Andalite morphing technology only works if the user "acquires" the DNA of the target organism by touch; fortunately, the acquiring process usually puts the target in a trance, so the Morpher doesn't have to worry about getting eaten or mauled. Over the course of the series, most of the main characters end up acquiring a sizable library of forms from across the animal kingdom, including several aliens, and Ax is even able to create his own unique human alter-ego by acquiring DNA from his fellow Animorphs. However, Visser Three takes the collection business to a new level, and actively seeks out deadly new forms on alien worlds for him to acquire — and use in combat.
- The Beyonders: In Chasing the Prophecy, we're introduced to the Guardian, a magical creature protecting the Celestine Library on Windbreak Island. While not a true shapeshifter per se, the creature does have the ability to take on the characteristics and attributes of different materials, making it quite formidable. The Guardian cannot mimic any material it has not come in contact with, but it can recall materials from its past, and it's been instilled with a sense of curiosity, driven to touch any unfamiliar objects it encounters so that it can learn its nature and mimic its form. The Guardian is ultimately defeated by this when the heroes trick it into mimicking a particularly volatile mineral that explodes when exposed to oxygen.
- Dragonlance: Sivak Draconians can shapeshift into anyone they've killed, allowing them to sow confusion amongst enemy ranks. They can only hold the form for a short while, but the timer resets if they kill again. Similarly, when they themselves are killed, they shift into the form of the person who killed them before dissolving into a pool of acid.
- Hagwood: The Werelings can transform into animals, but in order to manage a successful transformation, they need to have some understanding of how the animal in question actually works — meaning that they need to observe the creature in action. They also need a sample of fur or feathers from the target animal, which is to be kept in a pouch that must remain on their person at all times... and it's best not to get the samples mixed up. Gamaliel Tumpin gets his collection of samples muddled while trying to escape the villains at the end of Thorn Ogres of Hagwood, turning himself into a Shapeshifter Mashup — and accidentally saving his life in the process.
- Harry Potter: Polyjuice potion requires a physical sample (most commonly a lock of hair) from whoever you want to disguise yourself as. While the potion itself takes several months to brew, the hair can be added at the last minute if you don't have much time to pick your target. Unfortunately, this leads to a rather amusing misfire in The Chamber Of Secrets when Hermione uses a hair that she got from Millicent Bullstrode's robes... only to find too late that it was from Millicent's cat instead.
- Heretical Edge: Abaddon can store the forms of people he's possessed and shapeshift into them. Being a Blood Knight, he doesn't care about using it for infiltration, instead favoring the forms with strong and/or versatile powers. He has a limit of thirty stored forms at a time, but he can choose whether or not he adds a new form (and drops an old one) whenever he possesses someone.
- Jane Yellowrock: Skinwalkers such as Jane need DNA from a given animal (usually from bones) in order to shapeshift into it. But they have to deal with the Shapeshifter Baggage in that they can't assume larger forms without stealing mass and can't take smaller forms without storing it.
- Kroniki Drugiego Kręgu: Dragons need a "pattern" of whatever they're changing into... along with a lot of food beforehand (or they start "eating up" any surrounding matter).
- In The Licanius Trilogy, shapeshifters can only assume the shapes of people they have personally killed.
- Patternist: Anyanwu can analyze an animal's DNA by consuming a fragment of its flesh, then freely use it with her unmatched Biomanipulation powers. She uses this both for Animorphism and for improving her own body; for example, after she first transforms into a dolphin, she retains its ability to conserve oxygen.
- Phantoms: The Ancient Enemy is capable of reshaping its liquid body into just about anything that it's devoured, unwittingly indicating that it's been alive for millions of years when it manifests as a giant Carboniferous moth. However, it also absorbs the memories of its victims, so it can take on shapes that exist entirely within the human imagination — hence the winged serpent that menaces the team at one point.
- Red Dwarf: Last Human: The Symbi-morphs can shapeshift in order to fit the desires of their masters, but only once they've been symbiotically bonded with them, so most of the shapes they can assume are essentially "learned" from the minds of those they've been bonded with. For example, Reketrebn initially has no human forms in its repertoire, manifesting only as a female dingotang and inanimate objects like sofas and excrement; however, once it bonds with Lister, it immediately gains the forms of Kochanski, Rimmer, Kryten, Lister himself, a whole host of human celebrities, and a horse — all of which are put to use in amusing Lister or in helping him escape Cyberia.
- In From the Cold: Anya/Jenny can only shapeshift into people she's sampled by touch; once she has a sample, it remains perfectly preserved for decades on end, meaning that she can still take on the forms of people she encountered over thirty years ago exactly as they were when first sampled.
- Power Rangers S.P.D.: The shapeshifter Slate can only take on the forms of those whom he's scanned the "bioprint" of, and pays Broodwing an exorbitant amount to gain the bio-data of Devastation, one of the Rangers' most powerful foes.
- Star Trek: Deep Space Nine: Changelings have to see whatever they're trying to shapeshift into before they can do so, and even then, it takes a bit of practice. "The Search Part 2" reveals that the Changelings used to travel at length in search of new shapes to mimic before the fear of persecution by "Solids" drove them into hiding; later, in "The Begotten," Odo presents the baby Changeling with geometric shapes so it can learn the basics of shapeshifting, and Dr. Mora excitedly discusses the possibility of showing it simple plants and invertebrates as its powers develop.
- Supernatural: The Leviathans require a sample of the target's DNA before they can assume a human shape.
- Tracker: Cole has to model his new physical form on someone and decides on a handsome human male in an underwear advertisement. By contrast, the escaped prisoners he's hunting down are more inclined to take over human bodies by touching them.
- Dungeons & Dragons: The rules for the druid's Wildshape ability in the fifth edition state that the druid must have seen a particular type of beast before they can properly shapeshift into it.
- Exalted: Lunar Exalted have three forms to start out with — their original human form, the form of their personal animal totem, and a war form in the shape of a monstrous humanoid version of the second. Any additional shapes are obtained by tracking down an appropriate creature, killing it, and drinking its heart's blood. A wolf-totem Lunar who wants to be able to turn into an elephant, for instance, will need to kill and consume an elephant.
- In Nomine: Users of the Celestial Song of Beasts can transform into animals, but need to personally observe an animal of a desired species at least once before taking its shape.
- Pathfinder: Downplayed with the spell Beast Shape, which requires a piece of the creature whose form is being assumed as a material component. In practice, a spellcaster's component pouch is usually Hand Waved to have all the non-costly material components they need, barring unusual circumstances.
- Transformers: the titular Transformers typically scan to gain their altmodes. Mostly they can do this themselves but there is a device called the Sky Spy that collects data for Transformers to provide altmodes.
- Aquaria, being a Metroidvania, involves the player gathering new abilities along the way — in this case via the learning of new songs. And in many cases, these songs don't simply enact some transitory effect, but instead transform the player, thus granting them new powers or properties. Thus, the player's collection of songs, growing as they advance through the game, becomes in large part a collection of forms.
- Blood Omen: Legacy of Kain: Kain has some impressive shapeshifting powers, but he has to find each form across the map before he can use them, including the ability to turn into a swarm of bats, a wolf, a cloud of mist, and an ordinary human being.
- Cassette Beasts: Rather than catching Mons, the player has to record them onto cassettes and shapeshift into them.
- Castlevania: Symphony of the Night: Alucard has suffered from a Bag of Spilling during his centuries-long sleep and has to relearn his old skills — including the ability to transform into a bat — by gathering artefacts from across the castle. Along the way, he also learns the ability to transform into a wolf and a cloud of mist by collecting other relics, while all three forms can gain additional powers from even more artefacts in the later areas of the game.
- Castlevania: Aria of Sorrow: Implied to be the case with the boss known only as "Headhunter." She normally looks like a headless woman in 17th century garb; however, by putting heads from her collection on her neck she can transform into different shapes. For example, putting the head of a lizard-like creature turns her into one and gives her the ability to climb walls. And she's vocally eager to add your head to her collection...
- Chrono Cross: Sprigg the Mystic can use her dopplegang skill to mimic any monster she's KO'd in battle (or any monster KO'd by someone wearing the forget-me-not pot), but the player needs to put effort into 1) putting her into the active party, 2) look for the specific enemy that is wanted for Sprigg's set, and 3) make sure she lands the killing blow.
- Destroy All Humans!: Crypto can disguise himself as a human being via the Holobob, but for this to work, he actually has to copy the form of a human NPC. What makes this a little chancy is the fact that you need to be close enough to see said NPC before making the copy, meaning that if you're not careful, they might be able to see you as well — endangering your disguise unless you can eliminate any witnesses as quickly as possible. Plus, unless you continuously buff your power meter by reading the thoughts of anyone within range, you will lose your disguise and you'll have to copy another one.
- Dragon Age: Origins:
- According to Morrigan, the art of shapeshifting requires you to observe the animal you want to transform into until you have mastered its form. Within the game, though, all you need is to be a mage and have Morrigan teach you the specialty at the camp: once you've got that, you can gain new forms simply by progressing along the skill tree like any other ability in the game.
- Upon finding yourself trapped in the Fade during the "Lost In Dreams" quest, players of all origins can learn the ability to shapeshift in their dreams. As a result, you can take on the forms of a mouse, a burning man, a spirit, and even a golem, gaining unique powers in each body; unfortunately, all four shapes must first be learned from the lost souls trapped across the islands of the Fade, and they will only teach you these new forms if you can rescue them from the demons tormenting them.
- In Fugl, you gain the ability to enter the world as specific flying creatures by getting close to the respective animals in-game.
- In Graffiti Kingdom, Pixel has to use the Graffiti Wand in this way, needing to swipe it at an enemy to capture its form for a limited time, allowing him to learn its attacks for his own creations. Defeating that enemy also has a chance at leaving a card that allows him to take that form permanently.
- Jade Empire: In order to learn one of the transformational styles of combat, you must defeat a member of the race you're trying to transform into. For example, if you want the horse demon transformational style, you must first defeat a horse demon.
- The Legend of Zelda: Majora's Mask: Each of Link's transformation masks must be gained from a quest.
- Mega Man ZX Advent: You gain the ability to transform into a given Pseudoroid after defeating them in a boss fight.
- Metroid: The X Parasites are shapeshifters that can mimic any lifeform... but they must first absorb DNA from that lifeform. This typically involves infecting a living host or absorbing the DNA from biomatter (as seen with the Core-X that absorbed Ridley's DNA from his preserved corpse). X Parasites that possess DNA of multiple lifeforms can change between their forms or even combine them into hybrid forms.
- Mortal Kombat: In many iterations of the series, Shang Tsung can only take the form of people whose souls he's taken.
- Minecraft: The Morph Game Mod allows the Player Character to take the shape and, with the right configuration, abilities or traits of any mobs killed, non-vanilla included. This can include being able to fly as a Bat or Blaze, gaining their Weaksauce Weaknesses such as sunlight or water, and even the player's max health getting reduced.
- [PROTOTYPE]: Alex Mercer can shape his body into all manner of weapons and armor, but if he wants to mimic another human being, he has to consume them first. Unfortunately, though he retains their knowledge, he can't archive the shape itself — as the next target you consume overwrites your previous disguise. The ultimate twist is that he does have one form archived: "Alex" is really the Blacklight virus in disguise, having unknowingly consumed the real Alex Mercer's body and adopted it as a Shapeshifter Default Form following his violent death at Penn Station.
- ShadowCaster provides new forms via obelisks scattered across the course of the game. Touch one — in some cases after first completing it with its capstone — and a new form is granted, with all its various abilities and powers.
- Shantae: The titular character's signature ability is transforming into animals by doing magical dances. This means she usually has to learn the dances first before she can transform into a specific animal. Unfortunately, she always seems to forget the dances after every game and has to re-learn them again in the next one.
- The Shapeshifting Detective: The titular detective can only transform into people they've already met; once the first meeting is over, though, Sam can replicate their targets in perfect detail, right down to the clothing - as is illustrated if you go so far as to participate in Zak Weston's nude photoshoot.
- Team Fortress 2: Normally, a Spy can disguise himself as any class at any time. However, when a Spy is equipped with Your Eternal Reward, the same action consumes a full cloak meter but he can disguise himself by backstabbing someone on the enemy team as that specific player.
- El Goonish Shive: Grace's alien DNA allows her to become or mix-and-match together any form she's had previously. However, she can only gain new forms by first being transformed by an outside force. This is quickly Exploited, however; her boyfriend is a Teen Genius with an alien Transformation Ray, so she's been given enough varied human forms by the end of the summer to be a full-on Voluntary Shapeshifter.
- Ben 10: The Omnitrix slowly acquires new alien species for Ben to transform into throughout the series by a variety of methods, but most commonly by scanning DNA from new species Ben meets.
- Chaotic: One way to obtain a creature card (which allows a player to transform into that creature during battles) is by scanning them in Perim, which usually isn't easy, as it often requires getting up close to powerful monsters who don't like being scanned by humans. Notably, scanning captures the creature in their current condition, which can affect their cards when used in battle, such as when Tom scans a weakened Maxxor.
- Gravity Falls: In "Into the Bunker," the Shapeshifter apparently needs to study a target by the sight before he can assume its form, hence why he's so obsessed with getting his hands on the Journal and the huge library of potential shapes it offers. However, once he has a new shape, he can alter it at will — to the point that once he's seen both Dipper and Mabel, he immediately makes himself into a horrific Shapeshifter Mashup of the two — so it's not completely cut and dried. Gravity Falls: Journal 3 reveals that the Author helped "Shifty" to learn new shapes when he was young by presenting him with pictures of animals, though he was careful to avoid showing him anything too dangerous; he also made sure not to let Shifty see him without a surgical mask, hence why Shifty never takes the Author's true form at any point in the original episode.
- Miraculous Ladybug: Chameleon is able to take on the appearance of anyone and anything she kisses. Doing this results in the victim falling asleep and also allows her to access whatever powers the victim may possess. Considering how she's defeated, her shapeshifting may not be entirely voluntary.
- Spider-Man: The Animated Series: Chameleon uses his illusion belt to take pictures of his targets in order to impersonate them. This can be a liability for him, however; when he tried to impersonate Nick Fury, he used a photo of Fury that, unbeknownst to him, had been inverted, so his disguise ended up with Fury's eyepatch on the wrong eye.
- Wild Kratts: Practically every episode, the Kratt brothers add one or two new options to their Creature Power Suits' slate of possible forms. Adding a new form to their roster requires a thorough observation of the species to be imitated in the field, plus Aviva's work to produce new Power Discs. Actual transformation requires them to make physical contact with the species in question, or at least its preserved fur, scales, feathers, etc.