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.
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. It might also be a way to Spot the Imposter.
Still and all, it works for the story.
- Played for Laughs in Durarara!! A vending machine flying through the air is enough for Kida to identify Shizuo Hewaijima at a 500 meter distance.
- 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.
- Inverted in Naruto. When Jiraiya goes to fight Pain, he assumes that it's his former student Nagato because they both possess the Rinnegan. However, when they start fighting, Jiraiya notices that Pain only uses Summoning Techniques, which wouldn't make sense, because Nagato has mastered every ninja technique known to man (or at least, every single one Jiraiya knew and taught him). It's the first of many hints that he's got the wrong guy or more accurately, it's not the real Nagato fighting him personally.
- Happens thrice in Tiger Mask:
- Early on, Naoto/Tiger Mask tells the tale of a Tiger's Cave wrestler who had decided not to pay half his wages to the organization and changed mask and gymmick to not be recognized: Tiger's Cave recognized him immediately anyway from his body build and fighting style, and sent their wrestlers to hit him in the head until he went crazy.
- During the Maskmen World Championship the mysterious Great Zebra comes to help Tiger Mask. Zebra consciously refuses to kick because he knows he'd be recognized immediately, but Tiger Mask identifies him as Giant Baba from the fact he almost used a kick but stopped himself at the last moment, getting him to notice his giant feet (the first thing he had noticed about him when they first met). There were other clues (the large size and such excellent technique he could have the upper hand in a deathmatch against Tiger's Cave wrestlers without using fouls), but refusing to kick was what got Tiger Mask's gears moving.
- When Tiger Mask goes fighting into Tiger's Cave underground fighting ring, Mr. X recognizes him from his style. There's a twist: knowing that if he changed mask and gymmick he'd have been recognized and killed anyway before he could even go on the ring he walked in using his Tiger Mask gymmick, and the staff laughed at the apparent joke and just sent him on the ring without verifying his identity, at which point they could not touch him unless he was defeated and unmasked. Mr. X suspected he was the real deal the moment he saw him with his mask, as he knew who he was dealing with (by the reaction it was over the top even for Tiger Mask, but still in the realm of possibilities), but as he arrived when he was already on the ring he couldn't do anything.
- Subverted when Tiger Mask fights his fake: the match ends with the Tiger V, Tiger Mask's third Finishing Move that he has only recently completed, but as the imposter had already imitated his gymmick, weight, voice and the rest of his fighting style the public cannot be sure that the fake didn't imitate even that. Turns out he didn't, and the one who won with the Tiger V was the real deal, but Big Condor can tell them apart because of the masks (Tiger Mask's has plastic fangs, the fake's has steel ones), not by the style.
- Fate/Zero: Beserker is a knight cloaked in a shadowy aura that obscures his identity, so it remains a mystery for most of the story. Saber finally guesses Berserker's identity when he is able to effectively block and parry her invisible sword, showing that he knows its exact length and shape, realizing that he has to be one of the Knights of the Round Table. He's Sir Lancelot.
- In Dragon Ball, Chi-Chi entered herself in the Tenkaichi Budokai as Anonymous to keep her identity a secret from Goku, who hadn't seen her since they were children. While Master Roshi couldn't figure out who she was, he immediately picked up on her use of his own Turtle School fighting style, which she got from her father Ox-King, Roshi's former student.
- In the Usagi Yojimbo story "Demon Mask", the Serial Killer antagonist who targets ronin (like Usagi) uses a unique slashing technique. Usagi later notices the local guards practicing the same technique and discovers that it's called the "Full Moon Slash", and their late former captain (who was murdered by a ronin in the past) was the one who taught them. Usagi puts two and two together and realizes that the killer is the late captain's father, who taught his son the technique, having gone insane with grief over his son's death and targeting ronin because a ronin killed his son.
- 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.
- Captain America 411-412 (vol. 1): Cap, Diamondback and Falcon infiltrated A.I.M. Island during an annual weapons expo (protected by international law), disguised as villians Crossbones, Mother Dark and Jack O'Lantern, respectively. Unfortunately for Cap, this was at a time where Crossbones had already agreed to fight five opponents picked by Batroc The Leaper, to prove he (Crossbones) was the best hand-to-hand fighter in their ranks. The fifth opponent was Batroc himself, who immediately let Cap know he'd recognized his fighting style, but he'd keep quiet if he (as Crossbones) threw the match. When Cap tries to choke out Batroc to keep him quiet, a cohort of Batroc's immediately blew the whistle on Cap from outside the ring. Cue dogpile on Cap.
- In Diabolik Natasha Morgan identified the false Walter Dorian (Diabolik himself) as the mysterious masked thief who had recently appeared in Clerville when he uses the same kick she saw the thief use on a security camera recording.
- An amoral cattle owner recognizes Lucky Luke by how he shot his gun out of his hand like last time.
- Members of the Vale Secret Service in In the Kingdom's Service use different weapons while on the job than they do in their day to day lives for this exact reason. Oobleck trains Jaune in knife fighting as knives are versatile, easily concealable, and vastly different than using a sword and shield. Presumably this also applies to distinctive Semblances.
- Later utilized when Jaune faces an Atlas agent while undercover. Jaune recognizes her stance as one used by Oobleck but can't verbally state that he's a VSS agent so instead uses another stance Oobleck teaches, knowing she'd recognize it.
- Lucius Malfoy in Dodging Prison And Stealing Witches recognizes Lord Slytherin as Voldemort (or at least, someone possessed by one of Voldemort's horcruxes) because they have an identical dueling style.
- Lampshaded in The Fifth Act. While discussing the swordsman who could best Sephiroth, Angeal asks Sephiroth if Cloud Strife could be someone he wronged in the past. When Sephiroth responds that Cloud's sword separated, Angeal and Genesis agree that such a unique fighting style would be impossible to forget.
- In this untitled Miraculous Ladybug fic, experienced fencer Kagami realizes that her class rival is one of the city's costumed superheroes this way.
The weapons might have been different, and the security camera footage was hardly the best, but Kagami knew the nuances of a persons fighting style; knew how they expressed themselves through combat. Every fencer had a hallmark; a signature they affixed to every battle with the tip of their blade. No two fencers fought the same; Kagamis ripostes were second to none, her mothers strikes were more Flemish than Italian, and her grandfathers kendo lessons shone through every thrust of her fathers foil.
- The Dimensional Drifter: Yuya makes the connection between Judai and Sora when he notices that both are experts in Fusion Summoning but are inexperienced with Action Duels. That's when he starts prodding Sora about his background, and asks Judai if they went to the same Academia, as this particular combination of skills is extremely unusual in the city Yuya's from.
- 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 recognizes 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.
- 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 helps 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.
- In Brotherhood of the Rose, CIA agents Romulus and Remus assume that Mossad is sending assassins after them, because they're using Israeli hand-to-hand techniques unique to that intelligence service. The two agents were sent by their CIA handler on a special course to Israel so they'd also learn this technique. However this turns out to be a clue of a different kind, when they belatedly realize they're being hunted by their own counterparts, Mossad-trained CIA assassins sent by their own handler.
- In the Witcher saga, Bonhart figures out Ciri's identity after watching her fight. As a competent swordsman himself, he realizes her deadly fencing is essentially improvisational, which was a hallmark of witchers' fencing. Given that witcher-trained girls were, shall we say, uncommon, the rest was more or less a formality.
- Helena Bertinelli identifies Oliver Queen as the Hood after fighting the Hood in one scene and watching Oliver fight in another.
- As a former member of the League of Assassins, Damien Darhk recognizes that Thea has the same training after watching her fight, and even jokingly asks how the current Ra's al Ghul is doing, unaware that he's talking to his daughter.
- During the wedding fight in the Crisis on Earth-X crossover, Oliver ends up fighting a masked man, wielding a bow and matching him blow for blow. Oliver has his suspicions about the identity of the attacker, which are proven right, when Oliver-X unmasks himself during their next encounter. It's a little strange that their fighting styles are identical, since Oliver's is based on a mix of what he learned on Lian Yu, from The Mafiya and the League of Assassins.
- 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, punch, etc.>".
- A mild example in Warehouse 13, where Helena explains how she figured out that Time Travel was possible. The night her daughter was killed in a home invasion, her maid tried to fight off the burglars. When questioning one of the burglars, she realized that the maid was using Kempo, Helena's favored fighting style, which the maid didn't know. Thus, she knew that she would one day build a time machine and use Mental Time Travel to possess her maid.
- Luke Cage (2016): Luke panics at the prospect of Shades (who was also a Seagate inmate and is now in Harlem working for Cottonmouth) recognizing Luke and revealing his true identity as Carl Lucas, escaped prisoner. For his part, Shades doesn't recognize Luke when they casually interact... until he witnesses Luke fight a bunch of Cottonmouth's men, and recognizes Luke's particular fighting style.
- Daredevil (2015): Matt Murdock visits Wilson Fisk in prison and is disturbed to realise he is basically running the place, shown when Murdock angers Fisk enough that Fisk reveals his handcuffs are loose and starts beating on Murdock and vowing to get his revenge on him and all his friends for putting him in jail once he gets out. Murdock manages to punch him in self-defence before getting out of there, and Fisk goes back to his cell...and it dawns on him that the last person to hit him like that was Daredevil, so he orders the files they have on Murdock brought in for a closer look.
- Power Rangers:
- Referenced in Mighty Morphin' Power Rangers. Faced with Trini and the Monster of the Week shapeshifted into her, Jason suggests they both attack him, as he knows the real Trini's fighting style. The monster actually gives himself away by being way too eager.
- In Power Rangers Wild Force, Alyssa's father discovers the White Ranger is his daughter when he sees her fight in full costume.
- Person of Interest. At the start of Season 4, Team Machine are hiding from Artificial Intelligence Samaritan. While handling the case of the week, John Reese does a Dynamic Entry with a Grenade Launcher, followed by a Bar Brawl with Destination Defenestration and Perp Sweating, only to be knocked unconscious and dragged out of there by Sameen Shaw, as he's doing all his signature moves which will only draw Samaritan onto them.
- Kamen Rider Gaim: Used as a plot point. Oren Pierre Alfonso (Armored Rider Bravo) interferes in a bout between Gaim and Zangetsu, claiming the latter completely lacked the elegance he had in prior fights, and then proves it via outmaneuvering and flooring him. He's right. Mitsuzane had been impersonating his older brother, Takatora, the latter of whom Oren had a mancrush on.
- Treadstone. A CIA agent is shown security video of some psycho who killed everyone in a 7/11 store. On further study however, he notes the smooth one-handed draw, the fast yet accurate shooting, and rather than just shooting from right-to-left like most right-handed shooters would, the shooter selected his targets on the basis of threat level—from the youngest and physically fit to the oldest—showing calm thinking under pressure. All of which fit a Treadstone Supersoldier.
- While Sting was away from WCW, the nWo introduced a fake Sting to try and convince people Sting had joined them. When the real Sting did return to WCW, he had abandoned his old Surfer Dude gimmick for a new "Crow" gimmick that even the fans didn't recognize him, much less the nWo...until Crow Sting attacked nWo Sting, leading to the nWo themselves to admit their Sting was a pale imitation compared to the real thing.
- 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 back to his good friend and future tag team partner Frankie Kazarian, who he was simply filling in for at the time due to an injury. This also caused something of a subversion 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 impostor.
- 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. In Fire Emblem: Radiant Dawn, Ranulf identifies him after fighting him in costume and out of costume, and also acknowledges his scent. After being told about his identity, Ike 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.)
- In Sleeping Dogs, Conroy, a member of the Triad branch you infiltrate comments that the player, Wei Shen, is good with his fists. He also says that he knew an undercover cop who was also good with his fists that they ended up torturing to death. He drops the suspicions when you start killing other Triad members since undercover cops aren't supposed to kill (Wei is a Cowboy Cop type and his officers are somewhat apathetic to the bodycount if he gets result).
- In Xenoblade Chronicles, Metal Face attacks Dunban with a move only used by his old comrade Mumkhar. In fact, the disguised character did this deliberately for the express purpose of taunting Dunban.
- 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.
- 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.
- 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.
- Multiple times when hiding his identity, Zuko tries to avoid firebending by fighting with swords instead. It doesn't always work out:
- In his guise as the Blue Spirit, he breaks into Admiral Zhao's prison and fights the guards with just his swords. His cover is blown when Zhao recognizes that Zuko and the Blue Spirit own the same pair of swords.
- 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.
- Jet tries at one point forcing Zuko to use his firebending so the people of Earth Kingdom would realise he's a citizen of the 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.
- The Gaang subverts this at one point, using airbending to mimic the effects of earthbending to fool some Fire Nation soldiers.
- Aang also intentionally did this (using the marble trick,) to prove he was The Avatar when captured on Kiyoshi Island. Unlike other examples, this lead him to being treated like a celebrity seeing as how he was the latest incarnation of said island's founder.
- 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.
- 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.
- Star Wars Rebels: In "Rise of the Old Masters", the Grand Inquisitor is able to figure out who Kanan's master was (Depa Billaba) based on his fighting style.
- 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.
- This case is less egregious than 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 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 (they first suspect that "their" Robin is either some kind of hologram or a robot). 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.
- Taskmaster tries to invoke this in one episode of Ultimate Spider-Man by impersonating a substitute gym teacher and using an obstacle course to identify Spider-Man. It could have worked, given that Taskmaster has the explicit ability to memorize movement patterns, if not for Peter's habit of under-performing in class to maintain his "clumsy nerd" persona.
- Played a bit tragically in Young Justice. Artemis gets into a fight with her father Sportsmaster while masked and undercover. She tries to reveal her true identity by having her telepathic friend share her childhood memories with her father, but he dismisses it as a trick. It's not until she beats him up that he recognises the combat style he taught her and stands down. Sportsmaster isn't the best dad.
- 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.
- While it takes an expert to identify a specific school or kata, even laypersons tend to notice if you're fighting like you've been formally trained in some form of martial arts, and this can draw unwanted attention if you're -for example- an undercover cop trying to gather intelligence in a Bad-Guy Bar when the shit hits the fan.
- Indeed, Special Forces soldiers working undercover/incognito (such as the SAS operating in Northern Ireland during The Troubles) will often receive training to help them 'unlearn' the advanced fighting techniques they have been taught (or learn to use unrefined, brawling techniques where appropriate), so that they don't stand out should they be involved in any fighting. If a random participant in a bar brawl handily dispatches assailants with Krav Maga, it naturally raises questions and tips people off that this person may not be what they seem.