Fighting Fingerprint

Alfred: Well, perhaps our cowled friend can persuade him otherwise.
Bruce: It's not that easy, Alfred. He's after Batman as well.
Alfred: But why?
Bruce: He fought Bruce Wayne and Batman. Fighting styles are like fingerprints. Kyodai knows that we're the same man.
Batman: The Animated Series, "Day of the Samurai"

A lot of people hide their identities. A lot of those people do so because they're doing dangerous things. Like fighting.

Of course, stories are only interesting where there's risk and drama and junk. One way to introduce some drama is to let someone figure out the hooded vigilante's secret. If you don't want to have the hero lose a fight and get unmasked, or do something stupid at a crime scene, there are other options. One of those is to have an opponent face or observe the hero fighting both in and out of the mask, and from that realize that they're the same person.

There's some truth to this. Fighting is one of those things you don't have much control over, so it's not like you can lie about the way you fight. However, fighting's a lot like dancing. It may come in different styles, but they're all working toward the same goal. It's not a fingerprint; it's a blood type.

Still and all, it works for the story.

This is a less meta-y trope than Tell Me How You Fight. Compare Cover-Blowing Superpower and Revealing Skill.


Examples:

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    Anime and Manga 
  • In Sailor Moon episode 100 (dubbed as "Individual Happiness"), Sailor Venus battles the Monster of the Week in a one-on-one game of volleyball — the ball is an energy sphere protecting the Pure Heart Crystal extracted from the monster's victim. In the climax of the fight, Venus makes a diving save that the half-conscious victim recognizes as the exact move that Venus performed earlier in her civilian identity.
  • Mobile Suit Gundam Wing Endless Waltz: Duo recognizes he's fighting Trowa when he recognizes his tactic of excessively firing all of his weapons at him.
    • In the second to last battle of the original Mobile Suit Gundam Wing, Quatre and Dorothy are each using the ZERO System (an AI mindlink that induces a pseudo-Combat Clairvoyance) to coordinate their respective sides' forces. Despite having very limited knowledge of each other beforehand, they simultaneously figure out exactly who they're fighting from kilometers apart.
  • Attack on Titan: Annie's ruthlessly efficient fighting style is unique. Because of it, Armin uses it as evidence that she is the Female Titan, and after she taught it to Eren, he manages to pull one over Reiner in their fight.
    • Eren lost the first Titan fight against Annie because he recognized her fighting style and was distracted when he realized Annie was the Female Titan.
  • Mobile Fighter G Gundam: Domon figures out that a cloaked stranger is actually Master Asia after he uses a piece of cloth for a weapon and strikes his signature pose.
  • In Magical Girl Lyrical Nanoha ViVid, Einhart comes to realize that, while Vivio has the same body as the last Sankt Kaiser, Olivie Sägebrecht, they are not the same person as their fighting styles are completely different.
  • In one episode of Yamada-kun and the Seven Witches, Yamada, a well-known delinquent around school who uses a trade-mark round-house kick to win a lot of fights, gets identified as himself after switching bodies with a female classmate when he uses the same kick in a fight.

    Comic Books 
  • Tom "Pie-Face" Kalmaku recognizes his friend Hal Jordan is Green Lantern because they have the same right hook.
  • In 52, Renee Montoya realizes that Batwoman is her ex-girlfriend Kate Kane because she uses the exact same punching technique (in addition to the other clues.)
  • In The Punisher 2099, Jake is fighting a supervillain villain named Hot Wire, who can digitize himself to interact with electronic systems. Jake performs a Punch Catch on him, which he counters by turning his arm and ramming his elbow into Jake's face. Jake is shocked because it's a move he made up himself and there's only one other person he taught it to—his son, Dean Gallows.
  • In one storyline of Usagi Yojimbo, Usagi encounters a masked Serial Killer who targets Ronin like himself. He later sees the local law enforcement practicing a technique the killer used called the "Full Moon Stroke", and Usagi realizes that the killer must have a connection to them. He puts two and two together and confronts the retired former chief of police who had been driven insane after his son, who also served as police chief and taught the "Full Moon Stroke" to his men, was killed in a fight with a Ronin.
  • In an issue of Captain America, Cap was undercover, entering a villain's fighting tournament where the prize was a dangerous MacGuffin. He had the misfortune that his first opponent was Worthy Opponent Batroc The Leaper. Batroc recognizes him after just a few moves, even with Cap consciously disguising his style, but tells Cap he'll keep his mouth shut if he throws the match. Since Cap can't afford to lose, he tries to play dumb and maintain the masquerade. An insulted Batroc immediately blows his cover and violence ensues.

    Film 
  • In Sherlock Holmes A Game of Shadows, Holmes and Watson deduce the identity of Moriarty's Dragon, Sebastian Moran, thanks in part to Moran's Improbable Aiming Skills. Moran assassinates someone with a rifle shot at a 650 yard range in a 7-8mph wind; Watson claims there are only half a dozen marksmen in Europe with enough skill to shoot accurately under such conditions, and when Holmes finds a discarded cigarette at the scene of the crime, he recognises the blend as the same brand of Afghan tobacco that Watson smokes and concludes the killer must be the only man out of that half-dozen to have served the British Army in Afghanistan.
  • Iin the Wachowskis' Speed Racer, Speed suspects Racer X of being his Long-Lost Relative Rex, because Racer X drives in the same distinctive way Rex did.
  • This is a plot point in the movie Undefeatable. The main villain (a Serial Killer who gouges out the eyes of women who resemble his estranged wife) practices a hybrid fighting style. The main character attacks a rival gang because she recognises one of the styles he used on one of the victims as the one they use.

    Literature 
  • In the Harry Potter series, the Expelliarmus Spell is this to Harry. Becomes a bit of a problem when he is supposed to be hiding behind several people disguised as him, because it help the Death Eaters to recognize their main target. It started out as just being one of the few dueling spells Harry knew, but it worked out so well for him initially that for the next several books he made little effort to learn more and almost always defaulted to casting it. This turned out to be a poor choice.

    Live Action TV 
  • Helena Bertinelli identifies Oliver Queen as the Hood on Arrow after fighting the Hood in one scene and watching Oliver fight in another.
  • In the Burn Notice episode "Comrades", Michael Westen (in one of his narrative spy tips) talks about the importance of knowing different fighting styles and remembering which one to use depending on your cover. In the episode he was posing as a Russian Mafiya mook and so had to use a fighting style called Sambo.
    Michael (voice-over): A fight is one of the quickest ways to tell if someone isn't who they say they are. If you say you are Russian but fight like an American, consider your cover blown, which means you better know Sambo, the mixed martial art of Russia. Of course, you also have to win the fight; a great cover ID doesn't help much if you're dead.
  • On Nikita, Nikita recognizes her opponent, even with the hood, because of his fighting abilities in the second season episode "Doublecross".
  • In the Intelligence episode "Patient Zero" Gabriel does this when he and Riley are ambushed by black-ops operatives while tracking the eponymous loose bioweapon test subject.
    Gabriel: Last time I felt a hammer strike like that was at Fort Benning, Georgia.
    Riley: So we just got our ass kicked by US Special Forces.
  • In an early episode of Chuck, Sarah recognizes the masked woman who attacks her in her apartment as "Carina" because she always telegraphs her punches. Or so she claims.
  • Eliot, the hitter on the Leverage team, often identifies opponents like this. One of his catchphrases is, "It's a very distinctive style of <knife fighting, fighting stance, punching, etc.>".

    Professional Wrestling 
  • It quickly became clear in what was supposed to be a rookie Battle Royal for the Ring of Honor academy trainees of Pro Wrestling RESPECT that Ninja was not quite himself. As the match went on, it then became obvious he wasn't a rookie at all but Austin Aries.
  • Subverted in TNA regarding Suicide. Don West had figured out through observing him that Suicide was Christopher Daniels and accused Daniels of using a mask to earn two pay checks from TNA. But by the time West had figured this out and Daniels had reappeared, he had given the Suicide suit to his tag team partner Frankie Kazarian. This also caused something of a subverion when once again, Austin Aries decided to steal another wrestler's identity. So many people had been Suicide at that point no one found it too odd to see him wrestling like Aries until the current Suicide made it clear Aries was not a "legitimate" inheritor and changed his name to Manik to distance himself from the Aries imposter.

    Tabletop Games 
  • In the Champions system, the ability to do this is called "Analyze Style."
  • GURPS has the Style Familiarity perk which you can usually get only by learning the style. The main benefit is partial immunity to Deceptive Attacks from fellow practitioner.

    Video Games 
  • Greil from Fire Emblem Path of Radiance immediately identifies the completely anonymous Black Knight as one of his former students after exchanging blows and hearing his manner of speech. Ranulf identifies him after fighting him in costume and out of costume, and also acknowledges his scent. Ike after being told about his identity confirms it after clashing with him out of costume and claims it makes perfect sense in hindsight because their fighting style is identical.
  • When Sora faces "Ansem" in Kingdom Hearts II completely concealed in an Organization Black cloak, he's able to guess that it's actually Riku based on fighting style and signature weapon.
  • In League of Legends, Yasuo is wrongfully accused of murdering his master because he was killed using a wind blade technique that only Yasuo is known to have mastered. (Also he was killed while he was believed to be alone save for Yasuo, who was supposed to be guarding him, but skipped out to fight against the Noxus armies. They do have a pretty good case.)

    Web Comics 
  • In this The Order of the Stick strip, Roy correctly guesses that the warrior the Order is fighting is not Thog, but is actually an imposter, by observing his fighting style. Amongst other things, the imposter relies on defence and counter-attack in contrast to Thog's offensive fighting style, and he also leads with his other foot.

    Western Animation 
  • Avatar: The Last Airbender: This is the problem with bending powers. They can only be mastered by the people of the Elemental Nation corresponding to them, meaning that if you use for example waterbending, you're sure to be recognized to be a member of the Water Tribe. This applies especially to Aang, who (as the title of the series suggests) is the last airbender, so if he uses his powers, everyone can figure out that he's the Avatar.
    • Jet tries at one point forcing Zuko to use his firebending so the people of Earth Kingdom would realise he's a citizen of Fire Nation hiding in their country. The reason why he knew Zuko to be a firebender in the first place is because his uncle used firebending to warm up his tea.
      • Zuko was also forced to out himself as a firebender while defending an Earth Kingdom village he was staying in from some Earth Kingdom soldiers who were abusing their authority. He was doing fine with just his swords until the leader of the group proved to be a strong enough earthbender that Zuko had to go all-out in order to win. Afterward he had to flee the village he'd just saved.
    • Another thing that can give an Avatar away is that they're the only one that can bend more than one element. Korra ends up exposing herself as Avatar this way in her first pro-bending match when she reflexively bends earth and water at the same time.
    • The Gaang subverts this at one point, using airbending to mimic the effects of earthbending to fool some Fire Nation soldiers.
    • The increased intermixture between the Four Nations in The Legend of Korra reduces this, however. While interracial relationships were obviously uncommon when one nation was functionally extinct and a second was waging a genocidal war against the entire rest of the world, the 70+ years of peace following the end of the first season - and the creation of Republic City, which isn't bound to a specific nation - saw at least a few. Mako and Bolin, for example, come from both Earth and Fire stock, and as such one is a firebender and the other an earthbender specifically a lavabender. And then thrown out the window entirely in season 3; after Harmonic Convergence, citizens of any nation can gain airbending; the majority come from the Earth Kingdom mostly because of its high population.
      • This trope is also what allows Tarrlok to realize that Amon is his long-lost brother, Noatak. When Amon de-bends him, Tarrlok recognizes the sensation as being that of his brother's bloodbending.
  • Sym-Bionic Titan had a situation like this. One of the team's acquaintances had a fighting style distinctive to the royal guard of Galaluna, which Lance instantly recognized because he is a member of the royal guard. It's strongly implied that the man in question was trained by Lance's long-missing father.
  • Teenage Mutant Ninja Turtles (2012): Michelangelo befriends a famous martial artist and learns one of his secret katas. When Splinter sees the move he immediately deduces that whoever taught Michelangelo must have been trained by the Foot Clan because it comes from his arch rival Shredder's fighting style.
    • Less Egregious then most, as a Kata is a VERY formalized training set of moves. While Shredder only sees the tail end...you actually COULD recognize a school by the kata.
  • In the Batman: The Animated Series episode "Night of the Ninja," the titular ninja figures out that Bruce Wayne is Batman after fighting him, because they both studied martial arts under the same master in the past and had fought before.
  • On Xiaolin Showdown Omi's old friend Jermaine arrives at the temple having become a xiaolin monk since they last met. During a sparring match between the two, Jermaine manages to beat Omi using a move called "Repulse the Monkey", which makes Omi suspicious because it's a move that had been used on him before—by super bad guy Chase Young. It turns out that Jermaine had been training under Chase, and was unaware that he was evil.
  • In Teen Titans, this actually works against Robin when someone new shows up wearing the Red X suit that he himself once used against his friends. After the entire team is effectively curbstomped by Red X, it takes some convincing for the other Titans to believe that it's not Robin this time. Why? Because the "new" Red X's fighting style is so incredibly similar to Robin's own. It never is revealed just who the new Red X is, or why their fighting style is so much like Robin's.