"Your shuriken pouch is on your left leg, but Naruto is right handed."Basically, someone has been body-snatched, copied or impersonated, but some mannerism, trick of speech or other attribute has been lost in the snatching/copying. Subtrope of Spot the Impostor. Compare to Something Only They Would Say and Bluff the Impostor. One result, and often the dead giveaway, of an Imposter-Exposing Test. See also Cover Identity Anomaly and Spotting the Thread. Expect spoilers!
— Sasuke Uchiha telling it like it is
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Anime and Manga
- In Magical Girl Lyrical Nanoha A's, when the masked men take on Nanoha and Fate’s identities, parts of their barrier jackets are not the correct color. This is likely because cats, and by extension Cat Girls, are colorblind. Not that it really matters, since the person they were trying to fool had never seen Nanoha or Fate in their barrier jackets.
- In Fullmetal Alchemist, Hughes is able to realize that Maria Ross is being impersonated by Envy because she doesn’t have her mole. This doesn’t save him from being killed, nor does it save Ross from being framed for his murder in the manga.
- A Rain Ninja impersonating Naruto puts his shuriken holster on the wrong side (having a different dominant hand) and doesn’t include the cut Naruto got from Anko. Sasuke says this lack of attention to detail makes the Rain Ninja worse than Naruto.
- Directly after this incident, Sasuke makes up a long and complicated password to serve as the one detail. Orochimaru later disguises himself as Naruto and recites the password perfectly. Sasuke immediately realizes that he's an impostor, as he forgot that Naruto was an Idiot Hero who could never have gotten the password correct on his first try (this being Sasuke's plan with the password all along).
- In a filler arc, Naruto, Kiba and Hinata invoke this trope to distinguish themselves from their impostors. They have Hinata, who injured her leg, stay behind, and have the real Kiba be identified by having Akamaru with him, and the real Naruto identified by the chest via carrying it like a backpack. Amusingly enough, at the end of the arc, Naruto sets down the chest for a moment and Hinata, noticing he doesn't have it with him, sends him flying with a palm strike.
- In another filler arc, the villains impersonate Hinata, but the fake Hinata doesn't blush when coming into contact with Naruto.
- In the Sasuke Retrieval arc, Shikamaru disguises himself as Jirobo and pretends to catch up with the rest of the Sound Ninja Four. When Tayuya scolds him for being late, he apologizes, but Kidomaru refuses to hand over the barrel containing Sasuke, saying that Jirobo would have scolded Tayuya for her bad language.
- A Rain Ninja impersonating Naruto puts his shuriken holster on the wrong side (having a different dominant hand) and doesn’t include the cut Naruto got from Anko. Sasuke says this lack of attention to detail makes the Rain Ninja worse than Naruto.
- In Bleach, Szyael makes clones of Uryu, Renji, Dondochakka and Pesche. Uryu and Renji’s clones’ hair is slightly different and they have markings on their eyes. Dondochakka’s clones have no spots on their backs. Pesche’s clones wear trousers rather than a loincloth. Szyael claims that this is not carelessness as much as modifying them to fit his tastes, and while Renji claims he is stupid for doing this, Uryu notes that Renji didn’t notice until he pointed it out.
- In Tsubasa Reservoir Chronicle, a minor antagonist tries to protect himself from Syaoran's attacks by claiming to have taken Sakura hostage. However Syaoran realises that the Sakura in front of him is just an illusion, since she calls him "Syaoran" instead of "Syaoran-kun". They're not in first name basis anymore; their past together has been written out of her memories as per the deal he made with Yuuko.
- In Detective Conan, there is a flashback episode where a grown up Shinichi is combating Kaito Kid (who can near perfectly disguise himself as anyone). Shinichi figures out which police officer Kaito was disguised as because he was the only one who remembered his own I.D. number. No one remembers their I.D. number.
- In Kinnikuman, Terryman attempted to masquerade as Kinnikuman to fight the Seven Devil Choujin while Kinnikuman recovered from his first bout with SteCasse King. He's quickly busted by being left-handed when Kinnikuman is right handed.
- Marine Boy: A false Marine Boy calls the real one's Dad by a variation of "father" the real Marine Boy doesn't use and this clues Marine Boy's Dad to the fact someone is impersonating him.
- In Dragon Ball Z, Semi-Perfect Cell tries to lure Android 18 to him by imitating Android 17's voice. He gives himself away when he praises Dr. Gero, unaware 17 and 18 despise the man.
- In a story of To Love-Ru, the target of the hitman Black is revealed to be an alien and master of disguise named Karmelon, who was disguised as a boy. Not giving up, Karmelon turns into Nana, hoping to throw Black and Yami off. But Karmelon's transformation backfires, as he forgets to copy Nana's chest size, which angers Nana into beating him to a pulp.
- The Spider-Man mini-series Spider-Man: Hobgoblin Lives!, Peter and Mary Jane are conversing about Ned Leeds, the man they all thought was the original Hobgoblin. However, as they were doing so, Peter realizes something he should have had ages ago: if Ned Leeds was the real Hobgoblin, the assassins that came in and killed him would have been the ones dead because he would have had the Goblin Formula in him. That leads to everyone realizing they'd been had.
- Prior to The Clone Saga, the Chameleon used synthetic androids disguised as his parents to discover Peter's relation to Spider-Man; these duplicates were almost perfect in appearance, personality, and almost memory, so much that Peter's Spider-Sense didn't go off until their suppressed programming did. The one missed detail occurred when they offered to take his Aunt May to Uncle Ben's grave on their anniversary. May had actually married Ben in a private ceremony a month before the formal one, and the only witnesses other than the priest were Richard and Mary Parker, Peter's parents; because the two androids didn't know the May's anniversary - something that could not have been programmed into their memory by the Chameleon nor anyone else - May suspected something was wrong, and this eventually led to the ruse being discovered.
- In The Smurfs comic book story "The Fake Smurf", Gargamel (and Hogatha in the Animated Adaptation) was capable of creating a formula that can change him into the form of a Smurf...but one detail that was missing in the transformation was that his impersonation doesn't have a tail. Gargamel tries to correct this by gluing a fake tail onto his behind, but later on the tail ended up falling off, and Gargamel was soon spotted and revealed to be the fake Smurf.
- Early in The Superior Foes of Spider-Man, Boomerang figures out that the gangster Hammerhead menacing him is actually disguised Chameleon, because Chameleon!Hammerhead was talking in a stereotypical gangster accent, and while that is Hammerhead's signature trait, the real Hammerhead had actually dropped the quirk at that point.
- This is what pings Lois Lane into realizing the Cyborg Superman isn't the real Superman in the "Reign Of The Supermen" arc of The Death of Superman - he casually mentions to Superboy that he wished he had better control of his powers when he was his age. Lois remembers that Superman didn't get his powers until he was an adult.
- Paperinik New Adventures
- During one of the many attempts of the Evronians to capture Xadhoom: after identifying her as a Xerbian, they lure her on a false Xerbian colony with the intent of tricking her into wearing a restraining device, but when a happy Xadhoom mentions their party should have a Xarghon and they don't know she sees through the ruse... And amuses herself with their attempts at guessing what a Xarghon is. When the Evronians finally catch on, Xadhoom informs them that a Xarghon is a traditional Xerbian welcome dance that any Xerbian child would have known of and promptly blows them up.
- In a less amusing instance, Paperinik disguises himself as Grigorji Grimka, son of Belgravia's president to infiltrate the country and find out who in the government had betrayed and was trying to kidnap him, but outs himself to Grigorji arranged fiancee when he tries to be gentle with her and offers her flowers, something the real one would have never done as he doesn't like her and knows she's allergic to pollen (and would have beaten him up had he given her flowers). Luckily, the fiancee is not the traitor but one of the loyalists, and they show up for the rescue at the decisive moment.
- Laff-A-Lympics: In "The Day the Rottens Won", Dynomutt figures out there's an imposter pretending to be Blue Falcon when he asks why Radley Crown didn't show up for the opening ceremony and the imposter, not knowing Crown is the real Blue Falcon, asks how he should know.
- In the Fresno, California-based Doctor Who Audio Dramas' continuity, the David Segal Doctor traveled with mute reporter Susie Jo Parker. Although mute, Susie Jo did speak. Usually when an impostor took her place and didn't research her very well.
- In White Devil of the Moon, the impostor, posing as Reinforce, referred to Hayate and Signum as 'the two of them' when the real Reinforce would have noticed that Signum was in Unison form, indicating the presence of a third person.
- In the Pony POV Series, Twilight attempts to repair Trixie's broken psyche, only to find herself with a psychiatrist who claims that she suffered a severe mental breakdown after accidentally killing Trixie completely and dragging the corpse around pretending it was still alive. Twilight starts to have suspicions when the doctor tells her that her "three friends" dumped her there, and moreso when the doctor can't understand why Twilight would think the Princess would care about this. Twilight is actually trapped by Trixie's subconscious, and Trixie never met Fluttershy or Pinkie, nor did she know about Twilight's official position.
- In Ojamajo Doremi Rise Of The Shadows, the Queen is able to figure out that it's not Majorin whom she's talking to but rather her Shadow, Evil Rin. She figures this out because Shadows in this fic do not cast shadows of their own. That, and she noticed something "off" about "Majorin's" behavior.
- In Waking Nightmares, Soldier, Derpy, Dinky, and Amethyst Star get replaced by changelings. The deception lasts less than a day before the protagonists wisen up to the inconsistencies (because the real Soldier never calls Spy a pervert [coward, sometimes maybe, but not pervert], Derpy hates English muffins, and Amethyst hates the Doctor due to some unspecified incident) and lead the imposters into an ambush.
- In the original Shadowchasers, Jinx is looking for the shapeshifting boggart in a wax museum (an incredibly dangerous situation, like looking for a needle in a haystack and the needle is trying to kill you). However, when she passes by a display representing the duel between Obi-Wan and Darth Vader in A New Hope, she notices that the Darth Vader statue has a green lightsaber, and realizes that must be him.
- In Shadow Realm PI, a fic set in the world of the Duel Monsters cards, someone frames the Amazoness monsters for her crimes by attacking people using an Amazoness Blowpiper's blow darts. One of her surviving victims realizes she was a fake because she was wearing high heels while the Amazonesses go barefoot.
- In Fly Me To the Moon: A Buffy Bayonetta Tale, Luka impersonates a soldier named Curtis to infiltrate a military base, taking great pains to look just like him and imitate his voice and mannerisms. Riley Finn spots him because his hands are smaller than Curtis' and perfectly smooth and manicured. Curtis fought and handled firearms his whole life, leaving his hands huge and calloused.
- In Equestria Girls: Friendship Souls, Grand Fisher attempts to lure in the Pie family by making his lure look like Pinkie Pie. Maud sees through it because "Pinkie" mentions she abandoned her friends to save herself from the Hollows, which Pinkie would never do. Maud also claims her scent is wrong.
Films — Animated
- Subverted in Toy Story 3. Barbie uses an astronaut suit to disguise herself as Ken to talk with the Bookworm. The suit covers her head and face, and almost her whole body...except her feet, and she forgot to change her high heels, which the Bookworm sees as she walks away. Fortunately, the Bookworm dismisses the high heels as one of Ken's idiosyncrasies.
- In Megamind, Megamind blows his cover in one scene by pronouncing Metro City to rhyme with "atrocity." He just barely avoids doing the same earlier in the film.
Films — Live-Action
- In The Sorcerer's Apprentice, sorcerers powerful enough to do so have the ability to morph into whomever they wish. When Drake Stone, a less experienced Morganian, attempts to trick Balthazar into giving him the Grimhold while disguised as Dave, he accidentally lets his British accent slip, giving himself away. He also forgot a second detail: the black nail-polish on the nails... which pretty much just confirmed the falseness of the imposter!
- In the movie Dead Again, a man claims to be the fiancé of an amnesiac woman and he presents a glove as proof. The glove seems to match the one the woman already has — a bit too well: it's for the same hand.
- In Harry Potter and the Goblet of Fire, Barty Crouch realizes that Mad-Eye Moody is actually his son when Moody licks his lips nervously, which is an established Character Tic for Barty Crouch Jr. Dumbledore figures out that this Moody is fake because the real Moody would never take Harry out of Dumbledore's sight after Harry arrived back in the maze with Cedric's body.
- After killing the Big Bad in the Total Recall (2012) remake, Doug wakes up in an emergency vehicle with Melina holding his hand. He then notices that she's missing the bullet wound scar on her hand, forcing his "wife" Lori to reveal herself (using a holographic device he used earlier) and attack him. This begs the question of why she didn't just kill him while he was sleeping.
- In The Master of Disguise during the climax, Devlin caught Pistachio in disguise as a henchman because he was still wearing part of his previous "Cherry Pie Man" disguise. That and he knows the henchman is not married.
- Though they're not impersonating one person in particular, the British spy in Inglourious Basterds is given away by the way he gestures to the bartender for three more drinks. A true German would have used his thumb, index and middle finger to denote three, while the Englishman uses his index, middle and ring finger.
- In Wild Wild West, Artemis Gordon has a nearly foolproof disguise as President Ulysses S. Grant (the fact that the same actor plays both helps) but West quickly knows it's not Grant because he was wearing the wrong school ring. It doesn't help that "Grant" keeps going on and on about how great an agent Gordon is.
- James Bond:
- In From Russia with Love, Grant pretends to be a British agent, but consumes red wine with fish, something a Brit would never do. He also says "Cheero" instead of "Cheerio". Bond doesn't put two and two together until after Grant gets the drop on him, then curses himself for missing it.
- In Thunderball, Colonel Jacques Bouvar Disguised in Drag as a rich widow. Bond spots him when he opens his car door himself instead of waiting for the chauffeur to do it.
- In You Only Live Twice, Bond disguises himself as an astronaut, but is spotted when he carries a piece of equipment that should always be carried by an assistant.
- In On Her Majesty's Secret Service, James Bond impersonates Sir Hilary Bray. The bad guys expose him when he is caught in his usual antics of seducing women. Apparently, the real Bray was gay or asexual.
- The T-800 in Terminator 2: Judgment Day calls John Connor's foster parents, and notices that the dog is barking wildly in the background. (It's been established earlier that dogs react this way to terminators.) He asks John what the dog's name is (Max), and then mimics John's voice, asking what's wrong with "Wolfie". When John's foster mom doesn't correct him, the T-800 concludes that John's parents have been killed and impersonated.
- The Dark Side of the Moon: Satan apparently forgot or didn't care that his host body is allergic to sugar in his coffee. It's down to just two crew members by that point, so the only remaining human immediately starts to prepare for the final confrontation.
- In Maximum Ride, the clone meant to replace Max has little knowledge of the flock, which means she doesn't know that Iggy is the Team Chef despite being blind, while she is supposed to be a terrible cook. Her cover is blown by the fact that six-year-old Angel is a mind reader, and was never fooled in the first place.
- This is the Fatal Flaw of the main antagonist of Needful Things. He cooks up fake evidences of crimes or slights and then plants them on people to turn them against each other, but he keeps getting small details wrong, either out of arrogance and negligence, or maybe for sport. For instance, the town's sheriff is shown an illusion of the death of his wife and child being due to a local hoodlum (in order to make him try to kill the man). The sheriff realizes it's a fake when he notices that they're wearing their seatbelts in the illusion - when not wearing them was what killed them in the first place.
- A Song of Ice and Fire
- The Faceless Men, a guild of master assassins, disguise their identities by a combination of glamour magic and acting skills. Part of their training, therefore, involves completely rejecting all traces of one's real identity, including name, family, and personality. Arya Stark is told off every time she gives herself away with the Character Tic of chewing on her bottom lip.
- Another Faceless Man was impersonating a poor student of the Oldtown Citadel. This student had a pet peeve: he hated being called a "pig boy", after a fairy-tale character of the same name as him. The Faceless Man, while introducing himself as that student, makes the mistake of calling himself "like that pig boy".
- In Allen Steele's The Tranquility Alternative, one of the first cracks in the imposter's assumed identity is when he doesn't respond appropriately to an elaborate online *cough* "roleplaying" scenario - such as not knowing that his virtual lover's fictional husband was killed off years ago. (An author's aside notes that the original would have told his captors anything they wanted to know... but they never thought to ask.)
- In the Ciaphas Cain short story The Little Things, Cain's first clue that the "waiter" bringing dinner to Amberley's hotel suite is a fake comes when he pounds loudly on the door — a room service waiter in a high-class hotel should have tapped politely. Finding that the man's uniform doesn't quite fit right just confirms it.
- In one of Aesop's fables, a literal Ass in a Lion Skin accidentally outs himself by braying. In another one, A Wolf in Sheep's Clothing accidentally outs himself by howling (although in other versions, the disguise works too well and he ends up slaughtered for food by the shepherd).
- In Going Down for the Count by David Stukas, the eponymous Count Siegfried von Schmidt has blue eyes and is an utter bastard. Manfred Weber, the man hired to impersonate and murder the count, has green eyes and is charming and romantic. Unfortunately for Manfred, the plan requires him to seduce hopeless romantic Robert, which he cannot do while better emulating the count, and the optometrist from whom Manfred purchased his color-changing contacts ends up mentioning the purchase to Robert. The discrepancies lead to Manfred and his employers being caught.
- This proves to be a fatal flaw in After the Funeral, a Hercule Poirot novel. When Richard Abernethie dies, his family gathers for the funeral and reception, at which point Cora Lansquenet, a relative, remarks "But he was murdered, wasn't he?" The next day, Cora herself is found dead, prompting the police to think that she was killed because she knew about the plot to murder Richard. Poirot himself begins investigating; all the while, Helen Abernethie is troubled by something that happened during the reception, but can't quite figure out what it is. Both she and Poirot eventually realize the problem—Cora was known for twisting her head to the right when she asked probing questions, but at the gathering, she tilted her neck to the left. It turns out that the "Cora" at the funeral was really her housekeeper and murderer Mrs. Gilchrist; she was trying to create the false impression that Richard was murdered to throw suspicion off herself. Unfortunately, she practiced her Cora impression in a mirror, and thus inadvertently reversed all of her motions.
- In the first book of Codex Alera, Fidelias figures out that a slave girl was really Lady Aquitainus Invidia because, even though she was shapeshifted via watercrafting, her body language was far more calm around Lord Aquitainus Attis than would be expected of an actual slave girl.
- Doctor Who:
- In "The Faceless Ones", Jamie is captured by the shape-shifting Chameleons and replaced with an imposter—who does not have the real Jamie's Scottish burr.
- In "New Earth", Lady Cassandra (who speaks in a rather posh fashion) takes over Rose Tyler's body. Aware that she doesn't sound like Rose, she asks her assistant Chip how she should speak to the Doctor, to which he replies "Old Earth Cockney". Hilarity ensues. She's later outed because (on top of the hilarity) she is not worried about the victims.
- In "Tooth and Claw", the Doctor accidentally ends up in the Scottish moors. The moment he realises they're in Scotland he switches to a Scottish accent (though not the actor David Tennant's natural Scottish accent) and pretends to be a Scottish physician named Dr. James McCrimmon so that Queen Victoria doesn't shoot him. Later at dinner he slips back into an English accent and Victoria calls him out.
- In "The Android Invasion", the Doctor can tell Sarah is an android because the android Sarah is wearing a scarf while the real one wasn't, and real Sarah hates ginger beer.
- Two telesnaps from episode six of "The Evil of the Daleks" show that this trope applied. When the Doctor named the three Humanized Daleks (using the Greek alphabet), he drew the lowercase letters on their shells. So when a Dalek bearing an uppercase Omega turned up, the Doctor knew it was a trap.
- In The Adventures of Superman episode "Tomb of Zaharan", Clark notes that a telegram supposedly written by Lois and Jimmy did not use reporter's phrases.
- The "Datalore" episode of Star Trek: The Next Generation made clear that Data doesn't use contractions, while Lore can. In an inversion, even though Data is the person Lore is copying, Data was the younger of the two, and so technically "lost" the ability to use contractions. (In a now-infamous mistake, the "real" Data used a contraction in the episode's final scene, and depending on who you talk to it either wasn't noticed or they didn't have time to do another take. This also launched a thousand, or at least half a dozen, wild mass guesses when it was noticed.)
- In the Red Dwarf episode "Psirens", the impostor Lister can play the guitar really well; the real Lister only thinks he can. In the same episode, Imposter!Kryten calls Lister 'Dave', while the Real Kryten always calls him 'Mr. Lister'.
- Tested in MythBusters when Adam and Jamie tried to disguise themselves as each other - despite much effort, vocal cues and accents ended up being the weakest part of the ensembles. Adam did better impersonating Jamie than Jamie did impersonating Adam, in part because Adam frequently mimics Jamie for amusement. That may have worked against Adam, however; while his impression of Jamie was better, it had also been used on-camera in the past, so the test subjects were more likely to recognize the "Jamie" voice as an impersonation by Adam.
- In the "body swap" storyline of Buffy the Vampire Slayer, Buffy had Faith's Bostonian accent on certain words. (No one really noticed in-universe.)
- Nicely done in Merlin (2008) when Morgana resurrects Lancelot from the spirit world, brainwashes him, and sends him to Camelot in order to stir up trouble. However, Merlin catches him out by phrasing a sentence that casually references the use of magic - Lancelot being one of only two people in Camelot who knows that Merlin is a warlock. But because Morgana doesn't know, then fake!Lancelot doesn't know either, and he responds in a manner that makes no sense from one who should be aware of Merlin's secret.
- Since Earth-2 Lionel is biologically the same person, he thinks that he can fully get away with seizing control of LuthorCorp from Earth-1 Tess. The only thing that's different between himself and his Earth-1 counterpart is that their fingerprints are opposites of each other. Earth-2 Lionel realizes this and reissues papers so that his fingerprints are on the new record, but he forgot one thing: since in his universe Tess was never given up for adoption, he overlooks the fact that all of the papers Earth-1 Lionel left at the orphanage with her have his fingerprints on them. This allows Tess to prove that he's a fraud and regain control of the company.
- In "Harvest", Clark loses his powers and he and Lois are held prisoner in a small rural village of religious fanatics who want to sacrifice them. They attempt to escape at one point by wearing the local clothing and walking out, but are caught because of Lois' nail polish.
- A season one episode of Sanctuary involved Magnus and Will being trapped in a crashed plane with a shapeshifting abnormal. Magnus discovers it when it's masquerading as Will when she asks for coffee instead of tea. The real Will would know that Magnus hates coffee.
- In Lost Girl, Inari shape-shifts into Kenzi and impersonates her after kidnapping the original. Bo exposes her after she casually eats peanuts, which Kenzi is allergic to.
- In season 5, Hera takes over the body of a dead man, returning to visit his wife. At first, it seems the wife believes in it when Dyson comes in (having seen the man dead already) and pressing Hera on her true identity (although Dyson does at first think it's Zeus instead). The wife comes in to offer a bag of marshmellows which Hera starts downing. She/he then grabs the wife by the throat and boasts about killing her before Dyson's eyes...only for the wife to stab Hera with a shard of glass she'd pocketed before. "My husband hated marshmellows."
- In the season two finale of Alias, Sydney offers Francie - or rather Allison, the spy who was turned into a double of Francie before killing her - coffee ice cream. "Francie" accepts, confirming Sydney's suspicion that she isn't Francie (who hated the stuff). All hell proceeds to break loose.
- In the season two premiere of Sleepy Hollow, Ichabod battles an evil Ichabod while rescuing Abbie from purgatory. The winner is about to leave purgatory with Abbie when he calls her "Lieutenant," as he always does... but he uses the American pronounciation, something the real Ichabod would never do.
- The Wild Wild West's "The Night of the Colonel's Ghost" has Artie impersonating Ulysses S. Grant in a bid to flush out a not-as-deceased-as-previously-thought colonel who's looking for hidden gold. Artie-as-Grant lists the battles the colonel and Grant fought in and all goes well - until he mentions a battle that took place after the colonel faked his demise.
- In the premier episode of The Player, this happens multiple times. Kane spots an assassin dressed as hotel staff because he's wearing the staff jacket but not the right pants. At the end of the episode he realizes it's not his wife's body in the morgue when he goes to place her wedding ring on it as the corpse doesn't have the ring tattoo around her finger that his wife had. No one else knew about the tattoo because it was hidden by the actual ring which she always wore.
- In the K.C. Undercover three-parter (or four-parter, depending on where you see it, as the hour-long first part was shown internationally as two half-hour instalments) "Double Crossed," K.C. has been kidnapped and substituted with a double as part of a revenge plan against Craig and The Organization. Marisa is the first to see something suspicious with her best friend when K.C. actually likes the idea of going to a party. Then, when K.C. mentions having something to do, Marisa asks if it's a spy mission, the imposter expressing surprise Marisa knows about her being a spy and Marisa realizes this isn't the real K.C. although she herself is snatched before she can do anything. The Coopers themselves find out when J.U.D.Y.-recorded surveillance footage reveals K.C. - a fervent vegetarian - eating meatballs. When the Coopers find K.C. and her double, the double tries to "prove" she's the real deal by relating a childhood story about K.C. However, that just proves she's the fake as the Coopers know the real K.C. was totally embarrassed by the incident and vowed she would never tell that story to anyone.
- Used in the Halloween Episode of Power Rangers Dino Charge: One of the six Rangers has been replaced by an Evil Twin duplicate, and Kendall needs to figure out which one it is. She uses a lie detector, but she's ultimately able to determine the fake based on one detail: Koda is the only Ranger on First-Name Basis with her, and he had repeatedly called her "Ms. Morgan" instead.
- Star Trek: Deep Space Nine: The Changeling who'd replaced General Martok for at least several months finally gives themselves away when they tell Sisko, O'Brien, Odo and Worf that in their attempt to kill Chancellor Gowron there shall be no "honor-duel". And Klingons are obsessed (usually) with honor. It's this that clues Odo in that Martok isn't who he says his is. The fact that he then attempts to murder Odo, in plain view of a dozen armed Klingons, also helps.
- One episode of Painkiller Jane had Jane imprisoned in an institution in a plot involving a shape-changer and rescued by friend Maureen. However, when changing clothes, Jane saw that "Maureen" was lacking a recent tattoo. Jane then forgave Maureen for sleeping with a classmate back at the FBI Academy, Maureen accepting the apology and since the guy had actually been the class geek, Jane knew this was a fake. The scheme is to trick Jane into exposing her team's HQ and when they drive up to a simple house, the imposter is confused. Jane then smiles "what's the matter? You don't recognize your own house?" The imposter realizes he's found out just as the real Maureen shows up to capture him.
- In an episode of The Librarians 2014, Stone finally reveals that he's a genius to his father, who never forgave him for leaving the family oil drilling business. His father gives him a heartfelt hug. After a moment, Stone explains that his real father would rather die than do something like that and jumps with the shapeshifter into a hole.
- In The Flash (2014), when Zoom has invaded Earth 1's Central City with an army of criminal meta-humans from Earth 2, Cisco and Caitlin try to trick the army's leader Black Siren (Laurel Lance's double) by pretending to be their villainous doubles (both already dead by that point) Reverb and Killer Frost, respectively. This appears to work, at first, then Black Siren tosses a random object at Reverb, and he catches it. Black Siren explains that the people of Earth 2 have the opposite dominant hand from Earth 1, and "Reverb" has caught the object with the wrong hand. Cue the Oh Crap! from Cisco and Caitlin.
- The traditional Japanese greeting "moshi-moshi" is a version of this. Shapeshifting youkai wouldn't be able to pronounce it right, giving themselves away.
- In Saints Row: The Third, The Boss attempts to impersonate Cyrus, the leader of STAG, but pretty much fails to act appropriately in any way. Given how poor the act is, it takes The Boss a surprisingly long time to get caught.
- For a period of time in between major updates, Spies in Team Fortress 2 suffered from this when disguising. Unlockable weapons for some of the other classes had been introduced, but Spies taking the disguises of other players of that class would only show stock weapons. Unlocks such as the Ubersaw and Blutsauger for the Medic or Backburner and Flare Gun for the Pyro were astoundingly popular choices and anyone not using them was suspect. For instance, Medics who appeared carrying basic Syringe Guns were immediately suspected as Spies, making the disguise even more difficult to use convincingly. This disguising oversight has since been patched out.
- A trait of a poor spy would also be always having their disguise carry the default weapon; its very odd indeed to see a Medic carrying a syringe gun over the medi-gun, or an enemy spy not to have a knife out. note
- Besides the above, there was one glaringly obvious tell once attached to the Medic disguise that made it completely unusable at the game's launch (which has long since been patched): When looking at a Spy-disguised-as-Medic, the "Ubercharge Built" meter didn't show up in their namebox like it would for a real Medic.
- Spies disguised as Scouts are also prone to "forgetting" how the latter class moves; Scouts are noticeably faster than other classes and can double-jump, which disguised Spies cannot.
- At one point in Bayonetta, the title character has to save Cereza from a giant Beloved angel. When the angel dies, Cereza falls into Bayonetta's arms... or, rather, the arms of a Joy angel mimicking her. The only giveaway? Angels can't hide their halos. A second giveaway is the fact that the Joy is fully clothed, despite Bayonetta being in the middle of a demon summoning at the time.
- In order to get into the black market in Ueno in Shin Megami Tensei IV, you have to say "Erewan" (in fact, the player has to type it into the game). Presumably this is a shibboleth designed to root out demonic infiltrators.
- Your clone in the Citadel DLC for Mass Effect 3 has more sort of forgotten every detail beyond "has the Normandy" and "wears an N7 badge"; doesn't have the charisma, doesn't have the flexibility, doesn't have the compassion, doesn't have the cybernetics, doesn't have a clue. You can actually point out, during the final confrontation, that there is no way the imposter is going to be able to fool, say, Admiral Hackett for even a minute.
- The imposter did, to their credit, remember that despite being a clone they would need to replace the original's recorded fingerprints with their own, and arranged a complex scheme to do just that.
- Star Trek Online: The side mission "Standoff" has the True Way try to frame a loyal Cardassian Self Defense Force gul as a traitor to Cardassia. The video that makes up part of the incriminating evidence turns out to actually be of a changeling in Gul Antos' shape, but the changeling got Antos' dominant hand wrong.
- In Banjo-Tooie, Mingy Jongo refers to Banjo by name (as opposed to Mumbo referring to him as Bear).
- In The Dragon Doctors, "Elizabeth", the leader of a gang of thieves, disguises herself as Goro with a specialized identity theft spell that hides her previous forms. Unfortunately for Elizabeth, Sarin instantly noticed that she couldn't see Goro's old male form.
- When Destania from Dan and Mab's Furry Adventures pretends to be Biggs to send her son Dan on a wild goose chase, she gets the hairstyle wrong on purpose to leave a subtle clue purely for sport.
- Parodied in Oglaf with the slutty master of disguise, whose otherwise flawless attempts at impersonation are always marred by his insistence on dressing as a slutty version of the person he's impersonating and claiming that he "won't sell out" when asked about it.
- Planet of Hats: How Spock is able to tell between Kirk and a man doing a good imitation of him. Only the real Kirk would unnecessarily rip his shirt in a fight.
- In Rusty and Co., the derro make a bunch of impostors of Stabs. Every single one of them, bar none, got something wrong — in some cases, dramatically so. The first one Presti runs into was pretty subtle (she was just missing the hair on her halfling feet), but Presti caught her out by asking about the makeshift bazooka she'd last left with the real Stabs; the impostor said it was too heavy to lug around (while the real Stabs would know it was enchanted to weigh very little.)
- In Jackie Chan Adventures, Jade is able to spot Paco as a magical clone because he pronounces her name correctly, unlike the real Paco, who always pronounced it "Yade." Truth in Television. There is no equivalent to the English "J" sound in the Spanish alphabet (their "J" sounds like an English "H"), so many Spanish-speakers even those who are basically bilingual still talk about watching Yaws or Yudge Yudy.
- Codename: Kids Next Door:
- One episode, when Numbuh One is trapped in a Lotus-Eater Machine, he realizes what's going on when he points out that Numbuh Four can't swim.
- In the episode "P.O.O.L.", Numbuh Four's friends are all replaced by evil twins from a negative universe originating from the pool. Hilariously, Numbuh Four fails entirely to spot that Numbuh One and Lizzie are fakes despite them acting very much like villains...but when he discovers that Numbuh Three has mean-looking eyes, that clues him in that his friends must be evil twins from another universe, because Numbuh Three would never look like that. Numbuh Four calls this deduction "being a friend!"
- My Little Pony: Friendship Is Magic:
- It's the principal failing of the Changelings, as "getting into character" isn't their strongest suit. More specifically, Fake!Cadance doesn't recognize the rhyme that she and Twilight used to sing; this is the first clue Twilight gets that something is wrong. In the IDW comics, a Changeling mimicking Derpy Hooves forgets to do the Fish Eyes. Another one has to smack it to make the eyes cock correctly.
- In the episode "Too Many Pinkie Pies", in order to separate the real Pinkie Pie from her army of duplicates, Twilight Sparkle and friends round them up and make them watch paint dry. Any one of them that gets distracted is destroyed - the real Pinkie Pie is the only one willing to watch something so boring for so long, since she would rather be with her friends in the future than have fun now.
- Episode "Spike at Your Service" features Spike doing favors for Applejack because she saved his life from Timberwolves. The girls decide to stage a fake Timberwolf attack so that Spike can "save" Applejack from doom. This didn't work because they forgot the bad breath that they have. Then the real Timberwolves show up and Spike end up having to save Applejack for real.
- In an episode of Batman: The Animated Series, Clayface tries to fool a security guard by shifting form into the likeness of the guy's boss, but the guard is tipped off when he realizes Clayface doesn't have an accent. (Then he remembers his boss is in Hawaii, and Clayface decides to skip the pleasantries and knock him out.)
- Clayface does it again in an episode of Justice League, while impersonating The Flash. He tries to bluff Batman into thinking he (Flash) had taken down Clayface. Batman immediately throws an explosive batarang at him. Turns out Clayface had overdone the slang.
Batman: You overplayed your hand, "yo."
- On Star Wars: Detours, the Decoys are supposed to look identical to Princess Leia in every way, but they're missing her most defining feature.
- In Spider-Man: The Animated Series Spider-Man is able to figure out that Nick Fury is actually the Chameleon in disguise after realizing he has his eyepatch over the wrong eye. (The Chameleon had gotten the disguise by looking at Fury's picture in The Daily Bugle, where a negative had been flipped.)
- Zigzagged in one episode of Ed, Edd 'n' Eddy (it happens, but the imposter still fools the victim). At the end of an episode, Sarah and Jimmy use a two-person costume to dress up like Eddy's brother in order to scare him, and then tell him to get them ice cream. Eddy is at first a little suspicious because his brother is lactose intolerant, but Sarah's acting is so convincing that he's scared into complying. Eddy's reaction is, or course, a Foreshadowing to the movie, where it's discovered how much he's really terrified of his brother.
- In an episode of Transformers Prime, Bulkhead manages to spot a fake Wheeljack by tricking him into telling a war story about Bulkhead, who was not actually present at the battle in question.
- In the Adventures of Sonic the Hedgehog episode "Tails' New Home", Sonic and Tails believe that they found the latter's parents and the former returns him to them. However, Sonic starts reminiscing about their first meeting and realizes he's been had - they kept calling him "Tails", not "Miles", his real name. Tails' "parents" were robots and he was captured by Robotnik.
- In Johnny Test, Dukey has to figure out which of two Johnnys are a robot. When they answer the first two questions perfectly, he asks a math question. One Johnny answers immediately, and Dukey blasts him. The reason being Johnny has to use his fingers when he's asked such a question.
- Pinky and the Brain: When Brain decides to take over the world by impersonating Abraham Lincoln, he's not worried that people will notice that he doesn't sound like the real Lincoln because Lincoln died before voice recording devices were invented and Brain doesn't believe there's any living person old enough to have heard Lincoln talk. The oldest living American proves him wrong about the last part.
- Static Shock: In "Duped", the shape-shifting criminal Replikon kidnaps A.J. McLean and steals his identity. Virgil and his friends eventually realize something is wrong because A.J.'s tattoos were on the opposite arms.
- Arabian Knights: In "The Spy," Zazum is accidentally separated from the Knights during a confrontation with Bakar's guards. A Shape Shifter in Bakar's army transforms into Zazum so as to infiltrate the Knights' home base. Unfortunately, he didn't learn the habits of "the real beast": when offered hay and an apple, he refuses both. Furthermore, when his tail is pulled, he doesn't bray and go into his tornado spin. Nida doesn't have this issue when she impersonates the changeling.
- The Simpsons: In "Krusty Gets Busted", with Sideshow Bob's eagerness to frame Krusty and send him to jail forever, he forgets a number of key facts that he knew about his co-star: He knew Krusty is illiterate, yet he is seen (via the security camera) reading a magazine at the counter, waiting for the store to clear out, and Bob (as Krusty) stood near a microwave oven, which Krusty can't do because he has an artificial pacemaker implanted in his heart (which was also captured via security camera). Naturally, when Bart points this out, Bob tries to bluff an explanation that Krusty was never very smart and liked to look at the pictures, but it sets up Bob's downfall.
- Older Than Feudalism: Shibboleths originate from biblical times and have been used throughout history to detect impostors (or people on the genocide list).
- For example: the words "brânză" and "cârpă" were often used to distinguish native Romanian speakers from native Hungarian speakers. In both words the "â" is pronounced as a close central unrounded vowel, while the "ă" is a schwa. Neither of these vowels exist in Hungarian, and many Hungarian speakers tend to confuse them.
- During World War 1, a British officer tried to fool an Askari of the German Schutztruppe in East Africa at night by giving him an order in Swahili. He got shot dead immediately because he could not disguise his British accent, specifically by the way English turns many long vowels into diphthongs.
- During World War 2, the forces of the Ustasha regime in Croatia were able to detect young Serbs (who belong to the Orthodox church) by telling them to make the sign of the cross. note
- During the Battle of the Bulge, Germans in U.S. uniforms infiltrated the allied lines. One of the quick ways to check out an unknown soldier was to ask him to say "squirrel".
- A similar test to spot Japanese saboteurs without coming close enough for a gander of their face was ordering them to say "Lollapalooza".