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[[quoteright:253:[[Disney/TheSwordInTheStone http://static.tvtropes.org/pmwiki/pub/images/shapeshifter04_8865.png]]]]
[-[[caption-width-right:248:"It's a battle of wits. The players change themselves into different things in an attempt to destroy one another."]]-]

->'''Merlin:''' N-now, Mim, no dragons, remember?!\\
'''Madam Mim:''' Did I say no ''purple'' dragons? ''DID I?''
-->-- ''Disney/TheSwordInTheStone''

There's nothing quite like the awesome brought to bear when a hero goes into battle with -- or as -- a {{Shapeshift|ing}}er, as they change forms and faces, [[ShapeshifterWeapon grow weapons and limbs]], or use camouflage to hide and strike.

Know what's better? A fight between ''two'' {{Shape Shifter}}s!

When two shapeshifters fight the only thing holding them back is their imagination and the versatility of their shape shifting abilities. Two similarly gifted shape shifters can play a deadly escalating game of Cat and Mouse [[EscalatingWar and Dog and Cougar]] [[{{Metaphorgotten}} and Manticore and Phoenix]] until one is finally outwitted and defeated by a form they just can't counter. Indeed, this is pretty much the ''only'' way for a shapeshifter duel to end. When compared with a normal fight, and even ignoring the HealingFactor issue, using blunt force trauma to win seems passé and overly prosaic. The winner is not necessarily the one who manages to get the biggest form; wits are more useful than brute force.

Alternately, the combatants will turn each other into undesirable forms to try to get the upper hand. This is usually PlayedForLaughs.

This is a recurring theme in myths and folklore, and is at least OlderThanPrint; folklorists call it a "transformation chase". There are a number of Celtic ballads, in particular, where a suitor pursues his chosen bride through a series of forms before she consents to marry.

TransformingMecha can often do a variant of this, but as they only have a set number of modes, they're allowed to pair up versatility with firepower.

Almost guaranteed to involve ShapeshifterSwanSong, OneWingedAngel, {{Shapeshifter Weapon}}s, {{Shape Shifter Mashup}}s and very often a variant of ElementalRockPaperScissors. Compare BattleInTheCenterOfTheMind. Contrast TrickingTheShapeshifter.



* [[https://www.youtube.com/watch?v=V2nL5sSSvd0 One]] {{Lego}} advert features this with a Lego cat and mouse rebuilding themselves into advantageous forms.

[[folder:Anime and Manga]]
* The manga ''Manga/{{Parasyte}}'' averts this by having its shapeshifting Parasytes almost always using utilitarian bladelike shapes rather than imaginative ones, and simply aiming to kill the other Parasyte's host before exhausting its own.
* A variation of this trope is played out in the Manga/GetterRobo series. In the ''Shin Getter'' manga and the ''Armageddon'' OVA, the Getter Team fights enemies with Getter Robo of their own, and win by luring their foes into rapidly switching between the Getter's forms, gaining advantage due to their skill and speed in completing their combinations faster.

* In ''ComicBook/TheSandman'', Morpheus fought the demon Choronzon in a poetry battle of sorts, where each sought to become something capable of defeating the opponent's previous form. Chronozon tried to trump Morpheus by turning into entropy, the end of all things. Morpheus won by turning into hope.
* The ComicBook/NewMutants became helpless bystanders when the Impossible Man dueled their member Warlock. As both characters are largely pacifistic, the bulk of the battle involved a "beefcake contest". [[spoiler:Impy was ultimately undone by his one weakness: he can't change color.]]
* A shapeshifting duel took place between Impy and Mr Mxyztplk in the IntercontinuityCrossover ''Silver Surfer/Superman'', in which they both took on the forms of heroes from their respective universes.
* Another one of these involving Impossible Man takes place in ComicBook/{{Exiles}}, when they visit an AlternateUniverse in which he can not only transform himself but also other things and went AxeCrazy after an attempt of a supervillain to take control over him had GoneHorriblyWrong. It ends with shapeshifter Morph dueling Impy and winning by making him laugh so much the brainwashing breaks.
** Morph gets into another one in mini-series ''X-Men: Die By The Sword'', with Mad Jim Jaspers. Sadly, we don't see too much of it.
* An erotic variation occurs in the ''ComicBook/XXXenophile'' story "Things That Go Bump in the Night".
* ''[[Franchise/JusticeLeagueOfAmerica JLA]]'' #88-89: Plastic Man v. Fernus (Martian Manhunter's EnemyWithin).
* In ''GreenLantern 80 Page Giant'' #2, Plas and Kyle amuse themselves while on monitor duty by pitting Plas's shapes against ring-conjurations. The winner is [[spoiler: Martian Manhunter, who sneaks onto the Watchtower, and convinces them they're being attacked by two separate alien monsters]].
* A particularly dark chapter of ''ComicBook/CaptainBritain'' climaxes with a duel between villains Mad Jim Jaspers and the Fury: since Jaspers has the power to [[RealityWarper alter reality at will]] and the Fury is a robot that can [[AdaptiveAbility adapt to virtually any situation]], it's pretty extreme to say the least. In the end [[spoiler: the Fury wins by shifting into a dimension where matter and reality don't exist, leaving Jaspers completely defenceless.]]
* In Creator/GeoffJohns's ''Comicbook/TeenTitans'' issue "Beast Boys and Girls", a MadScientist type is revealed to have experimented on children and animals to discern the link between human and beast. These experiments changed him into a shapeshifter along the same lines as Beast Boy, calling himself the Zookeeper (his skin and animal forms are purple). Cue epic throwdown in the middle of downtown UsefulNotes/SanFrancisco.
** In another issue, Beast Boy had to fight Madame Rouge's shapeshifting daughter. After a long string of transformations, during which she mocked him for being unable to choose a form she couldn't mimic, he settled for an old-fashioned knockout in his human form.
* ''{{ComicBook/Fables}}'' has a couple of magical duels involving Frau Totenkinder (the witch from Hansel and Gretel) and other powerful opponents, and shapeshifting is one of the techniques the combatants employ.

[[folder:Fan Fiction]]
* [[http://dc-nation.livejournal.com/159575.html Aurora "Fauna" Andersen versus Black Lantern Garfield "Menagerie" Logan]] in Roleplay/DCNation's version of ComicBook/BlackestNight.
* The ''FanFic/PonyPOVSeries'' has an example during the FinalBattle of the Wedding Arc in the duel between [[spoiler: Cadence and Queen Cadenza ([[AGodAmI Alicorn!Chrysalis]])]], with both constantly shifting species to try and gain an advantage over the other.
* ''Fanfic/UniverseFalls'': "Into the Bunker" naturally has a showdown between Amethyst and Experiment 210, but Amethyst's brute-force tactics prove to be no match for the more cunning Shapeshifter, especially when he resorts to [[ShapeshifterGuiltTrip more psychological tactics]].

[[folder:Films -- Animated]]
* Towards the end of the Disney movie ''Disney/TheEmperorsNewGroove'' both [[spoiler:Kuzco and Yzma]]have been unwillingly shape-shifted into animal-form, and they fight over [[spoiler: the potion which can turn ''one'' of them back to normal..]]
* ''Disney/TheSwordInTheStone'', as the page quote and illustration indicates. Madame Mim and Merlin engage in a wizard's duel that involves this. [[spoiler:Merlin beats Mim's purple dragon form by turning into a germ and infecting her.]]

[[folder:Films -- Live-Action]]
* In ''Literature/ArabianNights'', the story of Aladdin involves a battle between the Genie of the Lamp and the Genie of the Ring: It starts with Mouse vs Cat vs Dog and goes from there. [[spoiler: There was a part where the Genie of the Lamp turns into a fire-breathing dragon. To counter, the Genie of the Ring turns into a camel and ''[[CrowningMomentOfAwesome spits in the dragon's mouth]]''. In the end, Aladdin cheats and steals his opponent's lamp, gaining control of the Genie of the Lamp and winning by default.]]
* In an earlier movie that includes Aladdin, ''WesternAnimation/TheAdventuresOfPrinceAchmed'', a witch and wizard have one of these for about a minute before resorting to fireballs.
* An early version of ''Film/ANightmareOnElmStreet3DreamWarriors'' featured one of these between Freddy and Will.
* The climax of ''Film/LittleNicky'' sees Nicky and Adrian duel with their reality-warping magic.
* The final battle in ''Film/MortalKombatAnnihilation'' has [[spoiler: Liu Kang and Shao Kahn engaging in one of these. Though they only use one form.]]

* In ''Literature/{{Animorphs}}'', both the Animorphs and Visser Three have shapeshifting powers, so these are common enough. The most extreme example is probably in ''The Return'', where Crayak pits Rachel and Visser Three against each other in a gladiatorial battle and they both strategically change forms constantly throughout the fight.
* As quoted above, Merlin and Madam Mim in ''The Sword in the Stone'', both [[Literature/TheOnceAndFutureKing the book]] and [[Disney/TheSwordInTheStone the Disney version]]. In both versions, Merlin wins by becoming an infectious bacterium, though in the Disney version Mim is merely bedridden instead of killed. It's strongly implied that this is the standard format for a "Wizard's Duel".
* ''[[ForgottenRealms Cleric Quintet]]'' has one of these, though it's more a BattleInTheCenterOfTheMind. A cursed object used to [[GrandTheftMe possess people]], is fighting Cadderly's efforts to destroy it. Good thing he's strong willed.
* ''Literature/{{Discworld}}'':
** ''Discworld/TheFifthElephant'' sees two [[WolfMan lycanthropes]] jump between animal and human while tearing at each other and fighting with themselves for control. Ow.
** A dramatic Shapeshifter Showdown between two magic users in ''Discworld/EqualRites'', was {{retcon}}ned into oblivion when the setting and a combatant settled into far less flashiness than what was shown. The ''TabletopGame/DiscworldRoleplayingGame'' suggests it was actually more of a Mental Illusion Showdown[=/=]BattleInTheCenterOfTheMind.
* In the short story "Hardshell" by Dean Koontz (published in ''Predators''), the climax reveals to the reader that the titular detective and the killer that he's tracking down are both alien shapeshifters. [[spoiler:They engage in a shapeshifting duel, and it turns out that the criminal is younger and less experienced. Hardshell simply envelops it in an impervious shell and suffocates it, since they still need oxygen.]]
* Mercedes Lackey's Literature/ElementalMasters series:
** It is mentioned in a backstory conversation in ''Literature/ReservedForTheCat'' -- [[spoiler:the Cat of the title is actually the heroine's father, trapped in cat shape as a result of this duel.]]
** Between the heroine and villain of ''Literature/TheGatesOfSleep''. The Gates, the heroine makes a mental note of studying 'The Twa Magicians' (see the Music section below for details).
* A Kenyan story found in [[http://store.augusthouse.com/productdetails.cfm?SKU=5194 this book]] involves a boy who uses shapeshifting to con people by turning himself into a bull and letting himself be sold, then running away. Eventually he tries it on someone who turns out to be a more experienced shapeshifter.
* Ran and Eln get into this in Doris Egan's ''Ivory'' trilogy. The fight finishes when [[spoiler: Theodora hops off the sidelines and just flat out stabs Eln.]]
* In the climax of ''Literature/DoraWilkSeries''' second book, Loki and Badb fight this way, each trying to outwit another. One of them only manages to gain an edge over another only when [[spoiler:Faoilinara, goddess of those who turn into wolves, forces wolf form -- in which Badb is much more proficient than Loki -- on both of them.]]
* In the FairyTale ''[[http://www.surlalunefairytales.com/authors/asbjornsenmoe/farmerweathersky.html Farmer Weathersky,]]'' after the father has reclaimed his son, [[EvilMentor Farmer Weathersky]] tries to reclaim him, but the boy runs off, shifting his shape to avoid being caught. Similarly in ''[[http://www.surlalunefairytales.com/authors/grimms/68thiefmaster.html The Thief and His Master]]'', ''[[http://www.mythfolklore.net/andrewlang/423.htm Master And Pupil]]'', ''[[http://www.mythfolklore.net/andrewlang/121.htm The Magic Book]]'' and ''[[http://www.surlalunefairytales.com/facetiousnights/night8_fable5.html Maestro Lattantio and His Apprentice Dionigi]]''.
** In at least one version of the story, Literature/PussInBoots also features a limited version of this trope. Via a spell, rather than an inborn ability, Puss defeats the ogre and wins his castle in a shapeshifting challenge rather than an outright fight. He does this by reverting to normal as the ogre changes into a mouse.
* In ''The Doomspell'' By Cliff [=McNish=], shifting forms rapidly in an attempt to outwit each other is a part of the epic battle between Rachel and Dragwena.
* Lloyd Alexander's ''The Arkadians'' features one of these in an in-story folktale. It's quite convincing.
* ''Literature/TheDresdenFiles''. Near the end of ''Literature/TurnCoat'', [[spoiler: Injun Joe]] and the [[EldritchAbomination Skinwalker]] have one of these. And it is ''[[CrowningMomentOfAwesome awesome]]''.
* The Monkey King and the god Erlang in ''Literature/JourneyToTheWest''.
* In Creator/JoeHaldeman's novel ''Camouflage'', the showdown between the only two aliens on earth comes into fruition when Jack a.k.a. the chameleon decides to follow his natural killing impulse and faces [[ShapeshifterDefaultForm Rae]]/ Sharon / Jimmy a.k.a. the changeling. Rae's ruses include transforming her severed arm in a monster with metal nails, knuckles as eyes, and centipede-like legs; while Jack transformed in a more brute figure: a [[OneWingedAngel neanderthal]]. Since both of them are pretty much immortal the confrontation gets unabashedly gory, it finishes rather unexpectedly though when [[spoiler: the artifact (Rae's partner in action a.k.a her flying sauce) lunges over the chameleon, jailing and freezing him for further examination in their home planet]].
* In Sergey Lukyanenko's novel ''Star Shadow'', the main character has a symbiotic alien creature in him that grants him limited shapeshifting abilities. During a fight with a HumanAlien, one of his hands turns into a claw. Seeing this, his opponent reveals that he is a "metamorph" and turns into a "scaly, alien creature." The protagonist wins by allowing the enemy to bite him, after turning his blood into poison.
* Piers Anthony used a variant in his Adept series, in which two shapeshifters compete in a race rather than a head-on battle. The participants have a limited number of specified forms they can change into; it's how cleverly they can use these forms to circumvent obstacles along the course that determines which one wins.
* ''Literature/JaneYellowrock'' fights an evil SkinWalker who devoured the liver of its prey and was capable of taking on a vampire form along with the form of anything else it ate.
* Used at one point in the [[ForgottenRealms Cleric Quintet]]
* A Polish national epic ''Sir Thaddeus'' says common folk attributes this kind of powers to UsefulNotes/NapoleonBonaparte and Aleksandr Suvorov, who were supposed to fight in a duel like that in the middle of a battle.
* A duel between the heads of the FeudingFamilies in ''TheMagiciansOfCaprona'' takes this form.
* The Ursula K. Leguin short story ''The Rule of Names'' climaxes in a shape-shifting duel between two wizards, [[spoiler:one of which turns out to be a dragon in disguise]].
* In ''Literature/{{Krabat}}'', in a dream. Krabat as a bird is hunted by the evil master (also polymorphed). Krabat sees a well, turns into a fish -- but now he's caught in the well. Fortunately, [[LoveInterest the Kantorka]] is there to take him out. He shapechanges into a golden ring on her finger. Then suddenly a one-eyed nobleman appears. Krabat turns into one grain, which Kantorka throws on the ground. The master turns into a rooster -- but Krabat is faster, turns into a fox and bites him dead. The dream sequence is a reference to the original tale Preussler's novel is based on; the shapeshifter duel there is how [[spoiler: Krabat kills the Master off for real]]
* ''Literature/LukeSkywalkerAndTheShadowsOfMindor'' has a MindScrew-y sort of mind battle at the end in which the villain cuts straight to the ultimate form, a supermassive black hole. He swallows Luke without an effort... and Luke [[spoiler:becomes a white fountain]], which frees the Big Bad's minions, which has the side effect of killing the villain.
** During ''Literature/GalaxyOfFear'', the BigBad of the first six books and Hoole, the protagonists' uncle, are both shapeshifting Shi'ido. Regrettably, they never actually fight; Hoole takes on different forms for combat, but [[NamesToRunAwayFromReallyFast Gog]] is more inclined to infiltration. But in ''Clones'', well, there is an evil Hoole clone.
--> The two Hooles surged toward one another, but they moved so quickly that Tash could hardly follow. Her uncle shifted into the shape of a many-horned lizard, while the other Hoole transformed into some sort of giant snake. But by the time they clashed, each of them had morphed two or three more times, until the two combatants were a quivering mass of shrieking, shape-changing flesh.
--> Tash was awestruck. She had never seen her uncle so enraged, nor had she ever seen two Shi'ido fight. No wonder Hoole [[DissonantSerenity always remains so calm]], she thought.
* Shapeshifting demons are common in ''Literature/TheBartimaeusTrilogy'', being summoned by magicians to do their bidding. While they're rarely set against one another directly (the last time someone tried to order a demon to kill another one, it turned out they were friends, and the demon refused the order... [[StuffBlowingUp destroying himself and quite a bit of his surroundings]] as a side effect), fights are still fairly common as a side effect of whatever they're all trying to do. In these fights, plenty of shapeshifting goes on, of course.
* Howl and the Witch of the Waste have one in ''Literature/HowlsMovingCastle''.
* ''Literature/CreaturesOfLightAndDarkness'' by Creator/RogerZelazny has a duel between shapechanging gods Horus and Thoth. Instead of [[InformedAttribute expected shapeshifting]] Thoth keeps teleporting them, effectively changing the environment to keep Horus neutralized but mostly unharmed. Horus tries to grow extra arms faster than they [[ItMakesSenseInContext get disabled/get burned/eat themselves]].
** The climactic battle between Set [[spoiler:(better known as Wakim)]] and [[EldritchAbomination The Thing That Cries In The Night]] is essentially a superwarrior with a MorphWeapon against a planet-sized shapeshifter. No matter what The Thing becomes, Set finds the form that can wound it some more.
* Happens in ''The Story of the Second Dervish'' in ''Literature/ArabianNights'' where a princess fights a Djinn by the two transforming into different creatures and attacking each other; a lot like the Disney ''Disney/SwordInTheStone''.
* A downplayed example appears near the end of ''Literature/HarryPotterAndThePrisonerOfAzkaban'', when [[spoiler:Remus involuntarily [[OurWerewolvesAreDifferent turns into a bloodthirsty wolf]] and his friend Sirius has to [[{{Animorphism}} transform into a]] {{hellhound}} to restrain him]].

[[folder:Live-Action TV]]
* Subverted in ''Series/StarTrekDeepSpaceNine'' where Odo and another changeling fight conventionally at first and then basically start merging into each other and trying to take control over the other's body. The fight involves no forms other than the humanoid ones they start as and their natural liquid-states.
** Played straight in Creator/PeterDavid's ExpandedUniverse novel, "The Siege." David even mentions this in the introduction, noting that he wasn't restrained by a live-action TV show's budget.

* The Magnetic Field's tribute song to Robert Burns, "Wi Nae Wee Bairn Ye'll Me Beget," features one of these between a woman and her prospective suitor. It ends with him turning into God, and her winning by not believing in him.
* ''Child Ballad'' #44 ("The Two Magicians") is all about this, but with "duel" replaced by [[ShapeshiftingSquick "attempted rape"]]. Best performed by British folk-rockers Music/SteeleyeSpan on their ''Now We Are Six'' album.
* From the middle to the end, Music/ToriAmos's "The Chase" is a transformation chase between Tori trying not to be killed by Anabelle (representing the spirit of the Hunter). It doesn't take long, and it doesn't really end well...
--> '''Anabelle''': Use your head or you'll be dead.
* [=ASPs=] ''Verwandlungen I -- III'' is about a Shape Shifting Battle between Literature/Krabat and his master. It ends when [[spoiler:the master [[StakingTheLovedOne kills Krabats Loved One]]]].

* In Myth/KoreanMythology, Haemosu the sun god and Habaek the river god fights in this way until the latter admits defeat.. and acknowledges him as his son-in-law. This seems to be standard fighting method for gods and demigods, since [[http://en.wikipedia.org/wiki/Suro_of_Gaya King Kim-suro]] and [[http://en.wikipedia.org/wiki/Talhae_of_Silla Seok-talhae]] also fought this way.
* The [[Myth/CelticMythology Welsh myth]] of Ceridwen and Taliesin has one that ends in a pretty unusual way. After being repeatedly foiled, Taliesin becomes a grain of wheat to [[NeedleInAStackOfNeedles hide among all the other grain]], but Ceridwen just becomes a hen and eats all of it. Then, because symbolism in mythology is more important than anatomical feasibility, she gives birth to him. Having become his mother, she can't bring herself to kill him and merely [[MosesInTheBulrushes casts him out to sea in a bag to be found and raised]].
* OlderThanPrint ''The Literature/ArabianNights'' examples:
** This happens in a crazy sequence during the second Tale of the Kalandar Prince.
** Another one is in "A Tale Of Porter And Girls" -- princess duels with Irfrit, resulting in both of them turning into fire and dying.

[[folder:Newspaper Comics]]
* ''ComicStrip/CalvinAndHobbes'', kinda -- in the first test of the [[TransformationRay transmogrifier gun]], Hobbes zaps Calvin into a (scientifically accurate) 2-foot pterodactyl. So Calvin zaps Hobbes into a duck, so Hobbes zaps Calvin into a pig, so Calvin zaps Hobbes into a monkey, so Hobbes zaps Calvin into a daisy, so Calvin zaps Hobbes into a crocodile, so Hobbes zaps Calvin into an armadillo... cut to "much later", where an owl and a hobgoblin are sulking and wondering who is which.
* ''ComicStrip/{{Zits}}'', combines the above with VolleyingInsults due to its love for illustrating metaphors: "Who are you calling a chicken? You pig!"

[[folder:Tabletop Games]]
* A ''Magazine/{{Dragon}}'' article from the days of 1st Edition AD&D described how druids would fight duels for the chance to advance to their class's upper levels. It recommended that attaining the highest level should mean winning a Shapeshifter Showdown against the incumbent Grand Druid.
* ''TabletopGame/{{GURPS}}'': Both ''GURPS Arabian Nights'' and ''GURPS Celtic Myth'' have discussions of the trope in relation to the respective mythologies, and how to handle it in games. The GURPS-based ''TabletopGame/DiscworldRoleplayingGame'' has rules for "Flashy Duelling in Magic" with the duels ''appearing'' to be shapeshifter showdowns.
* ''TabletopGame/{{Shadowrun}}''. An article in ''Shadowland'' magazine #5 on shapechanging mentions the "Shapshifter's Duel", where two wizards with shapechanging spells would do this.
* ''TabletopGame/{{Exalted}}'': When you play a Lunar and your nemesis of the day is someone from the Wyld, this is bound to happen. And the Lunars do fight TheFairFolk on regular basis.
* Fat Messiah Games's ''Shape Shifters: The Game of Transforming Wizards'' is entirely about this trope, with a large "tree of life" diagram showing the available shapes and the transitions between them, as well as their relative strengths and weaknesses.

* In ''VideoGame/KingsQuestV'', King Graham and Mordack have a shapeshifting duel. Eventually Mordack turns into a {{ring of fire}}, and Graham summons a raincloud, extinguishing him. Not that Graham is a shapeshifter, mind you. He just conveniently learns the four required spells (and only those four) just before [[GuideDangIt recharging his wand with a slice of rotten cheese]].
* While you aren't ''physically'' transforming, this is actually a major part of the newer ''VideoGame/{{Persona}}'' games. Each Persona has specific strengths and weaknesses, and the main character can shift through Personae to exploit his enemy's weaknesses while protecting his own. Certain boss fights (most obviously the [[spoiler:Nyx Avatar]] fight from ''VideoGame/{{Persona 3}}'', but also the BonusBoss from each game) involve shifting between Personae (in some cases on a turn by turn basis) to counter your opponent's attacks. Through clever manipulation of Personae strengths and weaknesses, you can take very little damage during a fight. (Except of course, when fighting a BonusBoss, as attempting to use a Persona with a "Null" or "Absorb" effect will result in a OneHitKill).
* In ''Franchise/{{Pokemon}}'', battles between two Ditto are tiresome. A Ditto is a blob-like Pokémon whose only attack is [[ExactlyWhatItSaysOnTheTin Transform]]. This allows it to shift into any opponent's form and use their attacks and stats for the duration of a battle. Catch is, it can only change into a copy of whatever opponent it is currently facing. [[DontExplainTheJoke One can fill in the rest]].
** In fact, if the battle is between two trainers who only have Dittos, the battle will ''never'' end (unless one Ditto is holding a harmful item). Normally, if two Pokemon are incapable of damaging each other, all you have to do is wait for them to run out of Power Points (using a move uses up 1 PP for that move, and can be replenished for free at a Pokemon Center), and then they will start using Struggle (which damages both Pokemon). But when Transform is used, the PP of all the copied moves is set to 5. Thus, using Transform on a Ditto will replenish your Ditto's PP, preventing either Ditto from using Struggle. And since you can't run from Trainer battles, you have to reset the game. (Thankfully, this was fixed in ''VideoGame/PokemonDiamondAndPearl'', as it is now impossible to transform into a transformed Pokémon.)
* In the first ''Videogame/SimonTheSorcerer'' game, once you learn some actual spells, you can challenge the Witch to one, complete with a ShoutOut to ''Disney/TheSwordInTheStone''. It functions as a game of RockPaperScissors: snake beats cat, cat beats mongoose, and mongoose beats snake. [[spoiler: And mouse enables you to escape through a hole in the wall when the Witch turns herself into a dragon.]]
* There are 3 of these in ''Project Altered Beast'' for the [=PS2=], first is a flashback sequence showing a fight between [[spoiler:Luke and Brad]] shown upon getting the Minotaur form, the second is an actual playable fight against [[spoiler:Brad]] and the third is against [[spoiler:Anastasia]]
* In ''VideoGame/WorldOfWarcraft'', druids of the opposing factions can do this in PVP. Since they can turn into bears with high defense, speedy cheetahs and seals (for water travel), damage-over-time-based big cats, and the occasional spellcasting moonkin, ''and'' they can all go back to caster form to heal themselves, you can occasionally have a spat with a single other druid that goes on for a very long time. These eventually turn into simply trying to chase the other one down and root them or making them exhaust their mana supply.
* [[Franchise/MortalKombat Shang Tsung vs. Shang Tsung]] kombats.
* In one scene in ''[[VideoGame/WeenTheProphecy Ween: The Prophecy]]'' the hero has to get past a shapeshifting dragon. The hero knows several forms, but the dragon always takes a form stronger than the hero's. [[spoiler:The solution is: become a worm to make him a wasp, catch him with a wasp trap, use outside help to dispose of the trap.]]
* This can sometimes happen during [[Film/TheThing1982 Changeling mode]] on ''[[VideoGame/SpaceStation13 Space Station 13.]]'' As demonstrated masterfully during [[http://www.youtube.com/watch?v=QLyXIg03opA&feature=youtu.be this episode of Razage's LP.]]

* Depends on the fight in ''Webcomic/ButImACatPerson''. With novice (or nervous) Masters, Beings are more likely to enter battle in a single form and stick with it, sometimes with the Masters [[http://erinptah.com/catperson/comic/chapter-four-page-4/ agreeing on that form beforehand]]. With more-experienced or more-daring Masters, or creative Beings whose options haven't been limited, look out for [[http://erinptah.com/catperson/comic/chapter-seventeen-page-7/ fast-paced and dramatic changes.]]

[[folder:Web Original]]
* [[FourthWallMailSlot Ask Vect]][[Anime/TransformersCybertron or Prime]] brings us [[http://tfwiki.net/wiki/Ask_Vector_Prime/Facebook_src#July_17 The tale of the Malignus and the Metrotitan.]] In the end [[spoiler:the Malignus tries to become entropy itself and explodes]].

[[folder:Western Animation]]
* The very first ''WesternAnimation/DextersLaboratory'' short had Dexter and Dee Dee zapping each other into various improbable animal forms with a remote Dexter had invented, ending with Dee Dee as Dexter and Dexter as Dee Dee.
-->'''Dexter!Dee Dee:''' Last one downstairs is an ugly, stinky, slimy spider!\\
'''Dee Dee!Dexter:''' Why not? I've been everything ''else'' today...
* ''WesternAnimation/JusticeLeague'':
** The Martian Manhunter vs. Clayface. Eventually, [[spoiler:the Martian wins on cleverness, by shifting into Clayface's natural form, and convincing the other villains to freeze his opponent solid before he could protest, waiting until a critical moment to reveal the trick.]]
** Justice League members faced off against their evil counterparts -- both Martians turned into long, serpenty things and... [[FightUnscene wrestled]].
** Justice League members faced off against their ''robotic duplicates'' of their evil counterparts. It's even more minimalist than last time, just a couple of seconds of grappling hand-to-hand in their regular forms.
** ComicBook/MartianManhunter finally get a much better one in ''WesternAnimation/JusticeLeagueDoom'' in his fight with Ma'alefa'ak.
* An episode of ''WesternAnimation/TheBatman'', "Clayfaces", invokes this trope when the original, reformed [[TragicVillain Clayface]] (Ethan Bennett) tries to help Batman stop the new homicidal [[GoingPostal Clayface]] (Basil Karlo).
* Some of the best fight scenes in the various ''{{Transformers}}'' series are the ones who know when to mix in a bit of this. ''Beast Wars'', for example, tended to use this during close-range combat.
* A shifting wrestling match occurred in ''WesternAnimation/StaticShock'' between [[RubberMan Rubberband Man]] and [[LivingShadow Ebon]].
* ''WesternAnimation/TheFairlyOddParents'': Cosmo and Wanda have a "magic fight" in one episode which involves turning each other into undesirable forms.
* One episode of ''WesternAnimation/Ben10AlienForce'' has Ben go up against Albedo, a former apprentice of Azmuth who had made a copy of the Omnitrix. Their fight involved just about all of Ben's forms between them. (Except [[AwesomeButImpractical Alien X]], naturally).
* In ''WesternAnimation/TeenTitans'', Beast Boy is pitted against an evil version of himself in the fourth season finale. Granted, a fair bit of it is offscreen, but the bits that they do show are really cool, especially when Evil!Beast Boy turns into an elephant, so Beast Boy turns into a mouse to frighten him. Played with in that neither Beast Boy is able to overcome the other, leaving this Shapeshifter Showdown a draw. However, ''none'' of the Titans are able to beat their own EnemyWithout, so they switch who they're fighting, and it's Cyborg who defeats Evil!Beast Boy via NoSell. [[CallBack Cyborg always knew he could beat Beast Boy]] [[RockPaperScissors (but of course, Starfire can beat Cyborg, and Beastboy can beat Starfire)]].
* In ''Walter Melon'', when Melon and Bitterbug are filling in for Lancelot and Arthur respectively, Merlin uses them to do this.
* A variation appears in ''WesternAnimation/DuckTales'' where Magica [=DeSpell=] had a bag of powder that turns whatever the powder is sprinkled on to whatever the err... [[PettingZooPeople person]] wants. The climax is Huey and the Beagle Boys fighting over the powder and transforming themselves and each other with it. It was awesome.
* Most fights between {{Transformers}} involve multiple shifts in and out of robot form. Justified, since their robot forms are better for fighting, but their disguise forms are more suited for transportation. Most fights were had while one side was running away from the other, or while they were vying for control of some [=MacGuffin=].
* Similar to the ''Fairly [=OddParents=]'' example above, one episode of ''WesternAnimation/SabrinaTheAnimatedSeries'' had Hilda and Zelda fighting by turning one another into undesirable forms.
* In the "Whimzee Come Home" episode of the ''{{WesternAnimation/My Little Pony And Friends}}'' side-series "Moondreamers", Whimzee has one similar to the "Sword in the Stone" example against the Queen of Imagination, but with magic amulets.