The physical version of SomethingOnlyTheyWouldSay, where a character is identified by an unusual body deformity or trait, like a mole or birthmark. Bonus points if the mark is in a place that would be embarrassing/forbidden to show in public.

See also ScarsAreForever. For a DistinguishingMark that marks the ChosenOne, see BirthmarkOfDestiny. If the Distinguishing Mark shows that the character is supernatural or magical, it's MarkOfTheSupernatural.
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!!Examples

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[[folder:Anime and Manga]]
* Subverted in ''MermaidMelodyPichiPichiPitch'', when Tarou notices a mermaid with RapunzelHair and is sure it must be Sara. It's not. ''All'' mermaids have long hair, and they otherwise looked nothing alike.
* In ''ChronoCrusade'', Chrono's missing horns are so prominent that he's known as "Chrono of the Broken Horn" to some of the other demons. And, of course, Satella is searching for a demon without horns...[[spoiler:But later it's revealed that ''Aion'' is missing his horns, as well.]]
* In ''LightNovel/HaruhiSuzumiya'', Mikuru's mole on her left breast is the usual thing Kyon looks for when he wants to see if it's the "real" Mikuru. In the novels, Kyon once asked her to show it (to which she replied with a punch) and another time realized it was ''not'' her because of it.
* In ''Anime/LuckyStar'', Konata looks identical to her mother, except for a birthmark under her eye (and her [[IdiotHair ahoge]]).
* Jacuzzi Splot from ''LightNovel/{{Baccano}}'' is often immediately identified by the blue, oddly-shaped sword tattoo on his face - unfortunate for him, considering that he's got a large bounty on his head and more than a few enemies with an axe to grind.
* A meta-example in ''VisualNovel/HigurashiNoNakuKoroNi'': the identity of the corpse discovered at the beginning of Curse Killing Chapter is never revealed, but an astute-eyed viewer can figure it out for themselves if they spot the DistinguishingMark -- [[spoiler:the red star-shaped tattoo on the left thigh identifies it as Rina Mamiya]].
* The easiest way to identify a [[Anime/{{Mai-HiME}} HiME]] is a fireball-shaped PowerTattoo on their body. It's in a different spot for each girl - Mai's is on her right breast, Natsuki's is on her lower back, etc. [[spoiler:Akira also has one, but she hides it to maintain her [[SweetPollyOliver disguise]], and thus the other [=HiME=] don't know that she's one of them until much later.]]
* Kotetsu T. Kaburagi/[[{{Superhero}} Wild Tiger]] from ''TigerAndBunny'' has a rather distinctive-looking [[BadassBeard goatee]]. In fact, it's ''so'' distinctive that it's implied that many people don't bother to remember what the rest of him looks like.
-->'''Security Guard:''' "With that beard and mask, anyone could look like him!"
* In ''Manga/FullMetalAlchemist'' Maria Ross has a mole under her eye. [[spoiler:While about to kill Major Hughes, Envy pretends to be Lt. Ross. Envy however fails to replicate this mark when imitating her but she quickly fixes it.]]
** Also, Scar got his nickname because of the [[CaptainObvious X-shaped scar]] on his forehead, courtesy of [[spoiler:Kimbley]]. We never actually learn his true name, but the other characters needed something to call him by.
* In ''Manga/{{Inuyasha}}'', the titular character has fuzzy, white dog ears on top of his head (not floppy ears like most dogs, more like the [[http://en.wikipedia.org/wiki/File:Shiba_Inu_cream.jpg Shibi Inu]] breed.) This marks his [[HumanMomNonhumanDad heritage]] as an ''inu-hanyou'' - half human, half dog-demon. He also his golden eyes with cat-like pupils, like his father.
** Most of the demons in the series show certain traits that tell them apart from humans, even when in humanoid form. These include pointed, elf-like ears, unusual coloration in their eyes and hair, and (sometimes) claws and fangs. If their true form has a tail, that will often be visible, since it apparently takes a lot of power to hide it.
*** In Shippouís case, hiding the tail is often a problem when he disguises himself using his fox-magic. (Shippou is a very young ''kitsune-youkai'' - fox demon. In Japanese folklore, foxes were said to be great tricksters, and the masters of disguise. Being so inexperienced, Shippou still isnít very good at shapeshifting, but heís getting better.)
* [[Manga/RurouniKenshin The Hitokiri Battousai]] is known for having red hair and a cross-shaped scar on his left cheek. In some places where he is less famous that gets shortened to just a cross-shaped scar.
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[[folder:Comic Books]]
* [[Comicbook/SonicTheHedgehog Princess Sally]] has a "royal birthmark". [[GettingCrapPastTheRadar Espio knows where it is.]]
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[[folder:Fanfiction]]
* In ''Fanfic/EmpathTheLuckiestSmurf'', Empath is distinguished from his fellow Smurfs by having a yellow star birthmark on his forehead, which according to their legend indicates that [[MarkOfTheSupernatural he has telekinetic and telepathic powers]]. Hefty in the series has a red heart birthmark on his right upper arm, but generally refers to it as a tattoo when he receives an identical mark on his left upper arm from Painter.
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[[folder:Film]]
* In ''Film/ThePrincessBride'', Count Rugen is identified by his [[RedRightHand sixth finger on his right hand]].
* There's a royal birthmark (the Purple Pimpernel) on the royal posterior of the true heir to the throne in ''Film/TheCourtJester''. Creator/DannyKaye's character gets to show the infant's bottom to everyone to gain their reverence.
* ''LAConfidential'': A mother cannot initially ID her daughter in the morgue. The Coroner prompts her with Detective Lieutenant Exley and Officer Bud White hanging on her every word:
-->'''Coroner:''' Mrs. Lefferts, does your daughter have any distinguishing marks?
-->'''Mrs. Lefferts:''' She has a birthmark on her hip. It's her. My baby!
:: The scene won the [[http://www.skinema.com/Skinnies1998.html 1998 Skinny Award]] for "Best birthmark used to further the plot".
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[[folder:General]]
* The [[ScannableMan barcode]] (which may be a tattoo but probably isn't) is often used as a sci-fi variation on the birthmark.
--> "Just pretend you're a box of cereal and I'm scanning your barcode."
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[[folder:Literature]]
* The ''{{Goosebumps}}'' book "My Hairiest Adventure" has a character with one blue eye and one green eye -- which [[ChekhovsGun turns out to be important]] after [[spoiler:she's transformed into a dog]].
* The Dragonlords of Joanne Bertrin's novels all have a distinguishing physical mark (birthmark, odd eyes, dwarfism, albinism) which indicates their Dragon natures. One of the clues that a young woman is not really a Dragon is that her mark can easily be hidden.
* ''Literature/HarryPotter''
** ''Literature/HarryPotterAndThePrisonerOfAzkaban'' uses the missing toe on Scabbers's front paw thusly.
** In ''Literature/HarryPotterAndTheDeathlyHallows'', Lucius Malfoy uses the scar on Harry's forehead to identify him, since Harry's face has been disfigured by Hermione's jinx.
** All of the [[{{Mooks}} Death Eaters]] have a Dark Mark branded on their arms.
* [[SilenceOfTheLambs Hannibal]] used to have six fingers on one hand, more specifically a second middle finger. He has it surgically removed after Silence, but of course he retains his [[RedEyesTakeWarning maroon eyes]].
* The Sylver family line in ''WelkinWeasels'' all have a facial birthmark shaped like a lightning bolt.
* ''ConanTheBarbarian'':
** In ''Literature/{{Jewels of Gwahlur}}'', Conan identifies a slave girl imposter by a birthmark.
** In ''Literature/AWitchShallBeBorn'', the witch can be identified by her birthmark.
* In Creator/ENesbit's ''Literature/FiveChildrenAndIt'', after the children foolishly wish that everyone would want their little brother and then have to chase after everyone who kidnaps him, one character claims him as his long-lost son because he ''doesn't'' have a birthmark.
* EdwardRutherfurd uses this trope a ''lot'' to distinguish between the families in his GenerationalSaga novels, variously giving them characteristics such as long toes, waddling gaits, or oversized noses. Played with a bit in ''London'', in which the Ducket/Dogget line has ''three'' such traits: natural SkunkStripe hair (both sexes), partially-webbed fingers (several of the males), or obesity that's probably linked to hypothyroidism (a few of the females).
* In the ''Literature/JudgeDee'' mystery ''The Chinese Maze Murders'' a father identifies his daughter's headless body by a burn on the arm that she got when she was just a toddler.
* The heirs to the throne of Riva in ''Literature/TheBelgariad'' have a white mark on their palms, burned into their bloodline when Riva Iron-Grip carried the Orb of Aldur.
* In ''Literature/ABrothersPrice'', part of the Porter family is polydactyl, with an extra toe on one foot. [[spoiler:This tips off Eldest Whistler to the paternity of Kij's daughter, Eldie, who was sired by Kij's brother Keifer. While Keifer was married to the princesses.]]
* ''Literature/TheMortalInstruments'': Jace Wayland has a star-shaped mark on his shoulder [[spoiler: which is a birthmark of the Herondale family.]]
** [[spoiler:Simon gains the ability to walk in sunlight, nicknaming him "Daylighter" and the Mark of Cain, though he later loses the latter.]]
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[[folder:Live-Action TV]]
* TheHero Rohan in ''Series/TheMysticKnightsOfTirNaNog'' has a birthmark called the Mark of Destiny that his druid mentor and foster father takes as a sign proclaiming him to be TheChosenOne. He's right... but the mark isn't unique to Rohan. [[spoiler: His half-brother Lugad and the BigBad Queen Maeve, ''their mother'', also bear the Mark of Destiny.]]
* PlayedForLaughs in the ''Series/{{Monk}}'' episode "Mr. Monk Takes On Manhattan", Monk recognizes a tiny mole on the perp's ear. He then spends an absurd amount of time describing the ear to a sketch artist. Later, when interviewing a suspect, Monk tries to get a peak at his ear.
* In an episode of ''Series/HotInCleveland'', a mother and son are reunited in part by the son bearing a birthmark on his wrist in the shape of a handbag.
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[[folder:Theatre]]
* Parodied in the one-act opera ''Cox and Box'' by F. C. Burnand and Arthur Sullivan, in which Box declares that Cox must be his long-lost brother because he ''doesn't'' have a birthmark on his arm.
* ''Theatre/AnimalCrackers'' identifies Roscoe W. Chandler as Abie the fish peddler with a large birthmark on his arm. Ravelli and the Professor later steal a wide array of his possessions - the Professor gets the birthmark.
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[[folder:Video Games]]
* ''ProfessorLaytonAndTheCuriousVillage'': Flora Reinhold's disappearing-reappearing birthmark is the final clue Layton needs to solve the mystery of St. Mystere.
* In ''VideoGame/KingsQuestIII'', the way Gwydion proves he's [[spoiler:the long lost Prince Alexander]] is by showing Princess Rosella a birthmark he has in a [[{{Mooning}} rather embarrassing place]].
* In several ''Franchise/TheLegendOfZelda'' games, the mark of the Triforce (see the featured image on the RuleOfThree page) appears on the hands of three [[TheChosenOne individuals]]. [[BigBad Ganondorf]] has the Triforce of Power, [[EverythingsBetterWithPrincesses Princess Zelda]] has the Triforce of Wisdom, and [[TheHero Link]] has the Triforce of Courage. Each piece of the Triforce is represented by a different triangle - Power is on top, Wisdom is on the bottom left, and Courage is on the bottom right.
** In ''VideoGame/TheLegendOfZeldaTwilightPrincess'', Link starts out with the BirthmarkOfDestiny on his left hand (right in the Wii version). Itís also visible in his wolf form.
* With the exception of Mark Meltzer or the multiplayer characters, all of the playable characters in the Franchise/{{Bioshock}} games have a mark or deformity on their hands or wrists.
** [[VideoGame/{{Bioshock 1}} Jack]] has a tattoo of a ball and chain on his wrists, [[spoiler: symbolizing the fact that he is a slave to Atlas/Fontaine.]]
** [[VideoGame/{{Bioshock 2}} Subjects Delta and Sigma]] have a Δ and Σ mark on their left hands, respectively.
** [[VideoGame/BioshockInfinite Booker DeWitt's]] right hand bears the mark of AD,[[spoiler: which are the initials of his daughter, Anna [=DeWitt=]]].
** [[VideoGame/BioshockInfinite Elizabeth]] has a missing phalanx bone on her right little finger, which she covers with a thimble. [[spoiler: The reason for this is that said phalanx bone was [[PortalCut cut off by a tear]] when she was an infant, thus allowing her to open tears.]]
* In ''VideoGame/FireEmblemAwakening'', the Exalted family of Yllise has the Mark of Naga on their bodies. Chrom has it on his shoulder, and his elder sister Emmeryn, her forehead. [[spoiler:Lucina, Chrom's daughter, inherites the Mark as well: it's found in [[MagicalEye the iris of her left eye.]]]]
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[[folder:Web Comics]]
* Nathan Hale in ''TheDreamer'' has a powder burn on his forehead and a mole on his neck.
* In ''Webcomic/ShinkaTheLastEevee'' Luna the Umbreon has diamond-shaped rings for some reason, her brother Shadow has orange instead of yellow rings and their clan banished him because of them.
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[[folder:Web Original]]
* ''SailorNothing'': Himei sports a black eye in Chapter 2; as she turns out, she can't [[ClarkKenting Clark Kent]] her way around it.
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[[folder:Western Animation]]
* ''GIJoe'': The difference between the mirror image Tomax and Xamot? Xomat has a scar on his left cheek.
* In ''WesternAnimation/ThePrincessAndThePea'', The court historian, Sebastian, makes a note that the newborn princess, Daria, had a heart-shaped birthmark on her left foot. This acts as a ChekhovsGun to help identify her as the real princess later on.
* Dipper of ''GravityFalls'' apparently has a birthmark on his forehead that looks like a certain constellation that answers [[WhoNamesTheirKidDude certain questions.]] He mentions that kids made fun of it before he started covering it up.
-->'''Wendy:''' The Big Dipper! ''That's'' how you got your nickname! I thought your parents just hated you or something.
* Cutie Marks from the various ''Franchise/MyLittlePony'' franchises: a unique symbol on the flank of every pony. ''[[WesternAnimation/MyLittlePonyFriendshipIsMagic Friendship Is Magic]]'' actually uses them as plot points: Ponies are born without them and receive one when they discover their special talent.
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