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Spot the Imposter

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Can you tell which one's which?

Leela: I don't know which one to shoot!
Fry: Flexo, shoot Flexo!

The heroes encounter a situation where the villain is an imposter of one of their own and/or a sympathetic character. The heroes must find out about the imposter and expose him/her to stop him.

Typically, the situation will involve the impostor and the real person standing side-by-side, both claiming to be the real one, and the other heroes must use their wits to identify who is who, usually by finding a quality that the faker doesn't have (in comedic examples, a positive quality). Or the real person may ask that their friend shoot both of them just to guarantee they get the imposter (and it's almost inevitable if the person has a super-healing power), which usually results in the heroes shooting the other one, because the impostor wouldn't be noble enough to suggest making the Heroic Sacrifice. This is often parodied these days where the imposter suggests it, knowing they'll assume the noble act to mark them out as the original — and sometimes double-parodied when this ends up outing him as the fake since the real person wouldn't be so noble.


In videogames, often the two clones will be desperately attempting to beat the crap out of each other while the player struggles to figure out a means of telling them apart, often with one tackling the other, punching him a few times until the pair rolls over and the person on top switches, ad nauseam (which conveniently allows a very short looping animation to represent the whole fight).

Speculative Fiction variants can get really confusing once you add in the possibilities of magic and/or Applied Phlebotinum: For example, the victim of a Body Swap must find a way to convince their friends that the person who looks like them really isn't, while the impostor is trying to convince the same friends that the victim is trying to initiate a body swap instead of undo one.

A common subversion is for the protagonist to either shoot in a blind guess that turns out correct, or simply shoot both and see who gets madder. In both situations, the victim of the imposter is likely to be incensed that the hero couldn't tell him from his doppelganger.


Another subversion is for neither of them to be an imposter but in fact both are two parts of the same person split with Applied Phlebotinum; see Evil Twin and Literal Split Personality. If they are two (visibly) different people but both claiming to be the 'real' whatever-position-would-be-relevant (captain, mother, president, owner, etc), see Judgment of Solomon.

A more comical subversion is when the imposter looks nothing like the person they are imitating, but people still act like they are identical, even if they haven't bothered with a Paper-Thin Disguise. The less the two look alike in this situation the more likely it is that no one can spot the difference.

May be caused by a Shell Game with people or when a Kill and Replace situation has occurred.

The No True Scotsman fallacy may come into play, when the protagonist knows the real John Doe's habits so well, the real John Doe would never do something so suspiciously out-of-character, such as the fake John Doe eating a cheese pizza, when the protagonist very well knows the real John Doe is lactose intolerant.

Compare Cover Identity Anomaly, Imposter Forgot One Detail (where the imposter's disguise has one subtle flaw), and Impostor Exposing Test. See also: Evil Twin, Bluff the Impostor, Confronting Your Imposter, Ten Little Murder Victims.


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    Anime and Manga 
  • Naruto:
    • During the Chunin Exams, two different characters use ninjutsu to disguise themselves as Naruto himself in the same episode, but one is identified as an imposter because he was left-handed (his throwing knife holder was on the wrong side), and the other reveals himself as a fake by repeating a long, complicated Trust Password that the real Naruto would never be able to remember.
    • During the Fourth Shinobi War an army of Zetsu clones disguise themselves as members of the army, even faking their chakra, and start picking off the enemy. Some are spotted based on mistakes in their cover identity, but ultimately only Naruto can identify them en masse due to his ability to sense their evil intent.
  • In one episode of Ghost in the Shell: Stand Alone Complex, a woman who has obsessively studied Pazu has a duplicate of his cyborg body made and her brain put into it; the two then fight and one ends up dead; the incident is not brought up for the rest of the series, implying that either the real Pazu won, or the fake was so good that she simply took his place.
    • Judicious use of the pause button, combined with paying very careful attention to details such as wounds inflicted at the start of the fight (when viewers still know which Pazu is the real one), make it clear that the real Pazu won the fight. However, the show lets you figure it out for yourself instead of spelling it out for you.
  • In Delicious in Dungeon, the party is confronted by a group of doppelgangers that have appeared in their image (based on each others' perceptions). Laios is the only one that is above suspicion, as all his doppelgangers look obviously fake. Through a process of elimination, they manage to narrow down the other clones to only a few options, but for the final ones, Laios decides they should all cook food to show that they're the real ones.
  • Mazinger:
    • In a Mazinger Z episode, Big Bad Dr. Hell fabricates a robot seems just like The Professor Yumi. However it was quickly identified by Sayaka when she noticed the imposter's nails were black. Dr. Hell used that strategy more times, creating a robot looked right like a secondary character and going as far as building a robot resembled The Hero Kouji. They also were spotted sooner or later.
    • That plot was partially reused in a Mazinkaiser episode. The Dragon Baron Ashura kidnapped Prof. Yumi and disguised himself like him. Sayaka suspected him nearly right away, though, because he tossed a birthday gift into a trash bin, and she told others her father would never do that.
  • Something similar occurs in the climax of Read or Die's OVA. By paying attention, it's possible to note that the "real" Miss Deep is the winner before it's revealed as part of the plot.
  • In an episode of YuYu Hakusho, Yuusuke is told that one of his friends is an imposter, and he must identify the imposter by punching them. He correctly chooses Kuwabara, but then reveals that he'd simply chosen the suspect who'd be best able to cope with being punched in the face. And the one who'd most likely fall into the trap allowing an impostor to appear in the first place.
  • Again the split was used in Ah! My Goddess, when Urd was split into her Demon and Goddess parts. Made easier when it turns out that Skuld had secretly put a mark on the goddess Urd.
  • In an episode of Rockman.EXE Beast, an evil alternate version of Numberman shows up infiltrating the core group of friends. When the normal universe's Numberman arrives, obligatory hilarity ensues as the two attack each other identically, to such an extent that their Dice Bombs roll the same number. The problem is solved when it's realized that if they attack both Numbermen, the fake one would be forced to shapeshift, and then all present Main Characters can hit him at once. note .
  • A variant occurs during the Frieza saga in Dragon Ball Z. Captain Ginyu uses a last ditch move that puts his mind in Goku's healthy, stronger body, while Goku's mind is stuck in Ginyu's injured form. The real Goku has to convince Gohan and Krillin what has happened when they attack him in Ginyu's body.
  • In Futari wa Pretty Cure, Poisonny impersonates Honoka at one point. When Nagisa has to pick the correct Honoka, all she can come up with is to ask them what her (Nagisa's) favorite food was, which is a question that has some problems. The Honokas proceeded to switch off saying accurate (and, for a time, increasingly negative) things about Nagisa, until the real one finally remembered that only she could read the diary in which Nagisa wrote that "my socks are a little smelly," a quotation that confused the fake. (The episode featured a Red Herring in the form of a perfume Honoka had made earlier in science club — as both Honokas pointed out, having or wearing the perfume proved nothing, because the fake could have just stolen the bottle.)
  • Subverted in Fullmetal Alchemist when Mustang and Hawkeye are confronting Envy. Envy pretends to be Mustang in front of Hawkeye. However, after a brief exchange, she points her gun at him and says she knows he's not Mustang because he was calling her Lieutenant, while the real Mustang always calls her Riza when it's just the two of them. Envy expresses surprise that the two of them are that close, at which point she tells him she was lying, but he'd already given himself away.
    • Played straight in the 2003 anime version. In the two-part episode "The Other Brothers Elric", the Tringham brothers pose as Ed and Al. In a variation, the Tringhams don't even resemble the Elrics (save for hair color), but no-one in the town knew what the Elrics look like; they just know their reputation.
    • When Envy poses as Ross, Hughes knows it isn't her when he notices she didn't have a mole under her left eye.
  • In Zatch Bell!, one of the characters has the ability to change into other characters... badly. He often has a way too big nose or forehead, but everyone but the one he transformed into is oblivious to the differences.
  • Pokémon
    • In "Will the Real Oak Stand Up?", with James from Team Rocket being the impostor. Interestingly, James was eventually discovered as the impostor not because he played his part badly but because he played his part too well: they were having a poetry contest, and James came up with overly-flowery poems to impress the judges. The poems were good, but they weren't even close to Professor Oak's actual poems, which were typically only two or three lines but contained a "hidden lesson" that was absent from James' poetry.
    • A later episode did the same thing, with the same imposter, with the same costume. They barely look alike. Nobody can tell the difference.
    • The Main Characters usually have a hard time seeing through James and Jesse's disguises, no matter how bad they are. However, in one Tournament Arc, Jesse tried disguising herself as Nurse Joy (there were several Joys at the stadium to handle the massive number of Pokémon) and Brock smelled a rat quickly; he swoons over every Joy he meets, and could even tell them apart (as he explained earlier in the episode) so it was easy for him to recognize a fake Joy, it seemed.
    • He's also spotted a fake Officer Jenny on at least one occasion, specifically because he only went ga-ga over the real one. That is, he subconsciously knew the impostor, despite being physically identical to all the other Jennies out there, was in fact simply a well-disguised man.
    • In another episode, Pikachu is surrounded by many ghostly illusions of Ash, with the real one lost among them. He settles the matter by shocking all of them, making them disappear until only the real Ash is left.
  • In the Alabasta arc in One Piece, Mr 2: Bon Kurei assumes the form of Usopp to fool Vivi. He fails because the crew was on guard, having met him before and had prepared a special sign to reveal their true identities. Not only that, but Bon Kurei in the guise of Usopp acts callous when Karuh is shot. Vivi knows that the real Usopp would never treat Karuh like that.
  • In Sumomomo Momomo, Iroha uses her clan's ability to turn into Momoko, voice and all. She gets touchy feely with Koushi when in the presence of Sanae so Sanae will not interfere with Momoko and Koushi's future marriage. The real Momoko shows up and Koushi figures the right one because Iroha is grabbing onto his arm which was just injured the previous episode and the real Momoko would know about that since she treated the injury. The real Momoko thinks the fake one is an assassin and quickly blasts her away. Iroha shows up about 5 seconds later without the disguise, but very bruised. Nobody ever figures it out or asks about it again.
  • Subverted in a filler arc of Bleach, specifically anime episode 326. While Captain Hitsugaya is fighting Reigei-Momo Hinamori, the real Momo appears and attacks Reigei-Momo. Hitsugaya has to figure out which one is the real Momo so he can defend her from Reigei-Momo's attack. Then, once he makes his choice, to his surprise the Momo he's protecting stabs him, revealing that both of them are Reigei-Momo. They then team up to try to kill him.
  • In Soul Eater, Maka becomes trapped in a room with a demon disguised as Soul, and the real Soul trapped in a box inside the room. The Fake!Soul explains to Maka that she has to open the box to get free (allowing himself to escape) with the real Soul's voice unable to reach her to warn her of the imposter. Maka is almost convinced until she points out that he had closed the door behind her, knowing they would be trapped, and that the real Soul would've immediately warned her to leave.
  • JoJo's Bizarre Adventure:
    • In Part 3, the group is on a ship and knows there's an enemy Stand user aboard, but whoever it is hasn't shown themselves. Jotaro, who's just finished smoking a cigarette, claims he's figured out the tell: when a Stand user inhales smoke, a vein pops out on their nose. Reflexively, all the heroes put their hands to their nose to check... and so does the ship's captain. In fact Jotaro was lying, no such tell exists, but the captain had given himself away with that action.
    • At one point in Part 4, Okuyasu has to figure out between two people dressed as Speedwagon Foundation members which is an assassin trying to kill Joseph, who's in the same room, with his stand (while the two look nothing alike, Okuyasu had never seen the assassin before and only heard him talk through his stand, and thus doesn't know what he looks or sounds like.) When the assassin discreetly preps his stand to attack, Okuyasu quickly punches him out, and when asked how he knew, proclaims that he's not that smart and was just going to punch out the other guy too.
  • Dragon Collection plays this trope straight a few times, both for drama and for laughs.
  • Fairy Tail: Heroic version. Earthland Erza manages to trick Faust and his soldiers before the Edolas-Erza shows up. Edolas-Erza cuts her hair later to keep it from happening again.
  • In The Seven Deadly Sins, the heroes get confronted by several magical duplicates of Hawk and Elizabeth. Meliodas simply smacks all of the Hawks at Super Speed. The real Hawk gets injured (and calls Meliodas out on it), but the fakes disappear. Meliodas then challenges all the Elizabeths to jump as high as they can. The fakes agree and do it, but the real one refuses because she is wearing a skirt and Meliodas stole her panties earlier.
  • My Hero Academia: After the UA students are separated during the Provisional Hero License Exam, Midoriya is alone against a team of students from another school when Uraraka shows up, and the two of them escape. Then Uraraka tries to tag Midoriya from behind and eliminate him from the test...and he swats her hand away without even looking. He knew all along that she wasn't really Uraraka, because she didn't use her powers to levitate when she fell off a ledge, and Uraraka would've never revealed herself to the enemy without a plan. Perhaps it would've been better to impersonate somebody Midoriya was less familiar with instead of his best friend, but the shapeshifter's power works by drinking the blood of the person they change into, and she extracted a pint of Uraraka's blood in the previous story arc but didn't have any other UA students' blood yet. There was also a visual clue for the readers to spot: the fake Uraraka was wearing her helmet, but the real one lost hers during the same attack that separated her from Midoriya in the first place.
  • Nagasarete Airantou: One chapter is about Machi trying to recapture a shapeshifting Genjumaro along with Ikuto and Suzu. It ends up with trying to identify it when it transformed into Mei-Mei. Ikuto manages to find it by making up a detail on her body. Except Ikuto was actually the Genjumaro. And the fake Mei-Mei was real Ikuto knocked out and transformed. Suzu suspects this since he was oddly accepting of magic during the search. Another unmentioned hint to the readers is when he wasn't nosebleeding while Machi was drying her clothes.

    Comic Books 
  • Spider-Man: This happens a lot when the Chameleon is involved. (He is a Master of Disguise, after all.)
    • A Fantastic Four and Spider-Man story resolves the situation of the Chameleon impersonating Spider-Man in a distinctive manner. The Thing, holding one in each hand, throws both several meters into the air. The Chameleon reveals himself by screaming in terror and the Human Torch flies up to catch him while the real Spider-Man, who is used to this kind of situation, calmly shoots a webline to swing to safety.
    • More than once, the Chameleon has wondered how it was possible Spider-Man automatically knew it was the Chameleon disguised as...Peter Parker.
    • One time after he discovered the hero's identity (and the fact that he was Kraven the Hunter's half-brother, something which gave him his confidence back) he impersonated Spider-Man and tried to fool Mary Jane. She realized it wasn't Peter when he kissed her; as she said herself, "It made my skin crawl." (This led to what was probably the most humiliating situation in the villain's career. Spider-Man didn't need to do anything; she beat him senseless with a baseball bat.)
    • Actually, the most humiliating might be when (after Peter revealed his identity to the world), the Chameleon infiltrated Avengers Tower as him, expertly fooling the various security scans. He then played at a dinner with Aunt May, eating some brownies and having some small talk while she knits. May then remarks about how "the real Peter only could have one or two almond brownies."
    May: You'll be interested to know that Peter's Uncle Ben could never go to sleep without making sure every single door and window in our house was locked and double-locked. And that Peter's favorite cookies are ginger-snaps and he hates oatmeal raisins, even mine. And that my friend Emily Pollack hasn't ordered yarn from me in ten years since she retired to Florida, the dear.
    Chameleon: were testing me the whole time?
    May: Heaven's no. I was confirming. I suspected you weren't Peter on the elevator ride up. After all...what kind of mother wouldn't be able to tell her own son from an imposter. Because that's what I am to Peter.
    • The Chameleon rises up to attack...only to fall flat on his face as May drugged the cookies. When the real Peter bursts in, he finds Chameleon all tied up as May keeps on knitting.
  • Gold Digger plays with this trope. Shapeshifter Madrid arranges to disguise herself as the Heroine, Gina Diggers. She then arranges for the real Gina to act out of character in several suspicious ways (an out-of-date outfit, etc.), while trapping herself for Gina's companions to find. As a finishing touch, during the confrontation with Gina, she uses the "lock us both up" subversion to win the trust of the others.
    • Later, one of Gina's friends (who happened to be Madrid's ex-husband) was able to determine she's the real one by telling her he'd fallen in love with her and asking if she loved him too. She apologized and said that while she valued him as a friend, she didn't feel that way about him, which convinced him she was the real one. He explained to Gina that one of Madrid's biggest flaws is that she never fails to tell someone what she thinks they want to hear.note 
  • In the Amazons Attack DCU Crisis Crossover, two Sgt. Steels have been discovered, and the government agency he runs need to figure out which is which. Finally, after a long interrogation, one of the Sgt. Steels in exasperation asks for a pen. The soldiers think it is for a handwriting test, but he instead points out that he has a metal arm, which doesn't bleed — and then swiftly stabs the other Steel in the 'metal' arm with a pencil, showing the second Steel to be a shapeshifter when he shouts out in pain. This is subverted, however, in that the first 'Sgt. Steel' is ALSO an imposter, one who has taken on Steel's form to discover where the real one is; he just happens to be an imposter who's quicker at thinking on his feet than the second one. Fortunately, the first one is the good guy.
    "Sgt. Steel": First, everyone knows that I have a metal hand. Second, metal doesn't bleed. Third, you're all fired.
  • Somewhat complicated version in a Nick Fury comic: Fury is battling Baron von Strucker, the head of HYDRA in his soon to be Collapsing Lair, but he has to disguise himself as Strucker using a convenient masking device in order to commandeer a plane out. However, he also sets up Strucker's death by first disguising Strucker as Fury and then putting a second mask on Strucker so he's wearing his own face on top of Fury's. Result? HYDRA troops burst in and see two Struckers fighting. Fury-disguised-as-Strucker convinces the HYDRA troops he's the real Strucker by yelling louder and ordering troops to remove Strucker-as-Fury-as-Strucker's mask, so the troops comply. Strucker panics and dives into the alpha particle generator, dying. Fury-as-Strucker jets off. A bit of Fridge Logic: Fury wears an eyepatch, while Strucker wears a monocle. Where did Fury get two eyepatches and two monocles from?
  • Archie Comics' Sonic the Hedgehog had an extended version in which the changes of Antoine were revealed to be him having been replaced with his Mirror Universe counterpart, who had promptly set to political maneuvering and nearly arranged to become king of Mobius before Sonic finally Spotted The Impostor. (Antoine, meanwhile, had been dumped in his counterpart's place and had been doing his best to play evil to keep anyone from catching on.)
  • In Supergirl (2005) Girl Power storyline, Dark Supergirl switches her costume with the original Supergirl’s at super-speed, in an attempt to fool Batman and Superman as to who was the evil clone. Superman tries to spot the imposter by punching both girls, assuming -wrongly- that the real one will not retaliate. Finally, the real Kara gets fed up with the situation, and tells Wonder Woman to use her Lasso of Truth.
  • An early Batman serial strip had Batman disguise himself as a mob boss in order to free Robin — unfortunately, the real one came back earlier than expected, and the boss' henchmen had recently decided to get rid of their Bad Boss.
  • An example occurs in the Batgirl Adventures Annual #1 comic where Batgirl is helping Harley Quinn track down Poison Ivy, who has been abducted. The villain manages to copycat Harley completely, from attire to voice, and Batgirl contemplates just beating up both of them. She finally figures out the real one when Harley uses her insult nickname for B(r)atgirl.
  • In the final issue of a short-lived mid-70s comic named after and starring The Joker, he decided to hold the heavily-insured feline sidekick of a famous movie comedian for ransom. The comedian disguised himself as the Joker in order to retrieve it, and when the Joker's minions were faced with this trope the Joker suggested that they let the cat go and whoever it went to would not be him. When it went to the Joker instead, and while being arrested he protested that a cat couldn't be trained to go to someone other than its master, the comedian said "No cat except my million-dollar kitty!"
  • A heartbreaking one during Marvel's Secret Invasion (the main mini-series): In Issue #8, Back from the Dead Mockingbird is confronted by her ex-husband, Hawkeye (who, at the time, was presumed dead and operating as masked hero Ronin). To prove she wasn't a Skrull, Hawkeye states a certain date, and asks Mockingbird what it meant. Turns out, Mockingbird had a miscarriage on that date and only she and Hawkeye ever knew she was even pregnant. This also served to tell Mockingbird who was under the Ronin mask.
  • G.I. Joe:
    • An early issue had Zartan trying to escape the Pit by disguising himself as various Joes... Until he tries to imitate Gung-Ho right before the real one shows up. When both of them end up in front of Sgt. Slaughter, he decks one of them, which shifts back to Zartan. Slaughter says it was just a lucky guess.
    • An early issue of the IDW reboot has him try to get into the team disguised as Snake-Eyes, only to get clocked by Duke. Duke didn't know he wasn't really Snake-Eyes, but was simply suspicious: If it had really been Snake-Eyes, he'd have easily blocked or avoided the punch.
  • Shows up extremely often in Diabolik due the titular Villain Protagonist having invented Latex Perfection. It's usually just a question to pinch someone's face to check for a mask, but sometimes even that it's not enough (for example, Diabolik may have an accomplice to impersonate someone with a different corporature, or look sufficiently like someone else to use different means).
    • Other times the spotting is made more complicated by the target preventing the police from doing the face check for some idiotic reason, something that always drives Ginko mad.
    • A scientist once invented a machine that could detect the presence of Diabolik's masks. At the end of the issue, Diabolik had destroyed the machine, killed the scientist and stolen the blueprints.
    • One of Diabolik's impersonations was that of Walter Dorian, a rich guy who looked just like him that Diabolik replaced to have a civilian identity (upon his second arrest, the one where they found out his real face, Diabolik ditched this as useless and confessed his murder).
    • Funny enough, Diabolik has been the spotting one in at least two occasions, where lookalikes hired by the mob impersonated Eva Kant to keep him distracted while they robbed him. The mob instructed the actresses to feign amnesia or being ill to justify the differences in personality that would have caused Diabolik to spot the difference at once. In the case of the fake illness, Diabolik was ultimately able to spot the imposter, but the amnesiac one was so good Diabolik had no idea until she confessed after learning the mob killed her lover (the surgeon that made her into an Eva lookalike).
  • Examples from the Disney Mouse and Duck Comics:
    • Mickey Mouse Comic Universe stories featuring Miklos, the Grey Mouse elevated this trope to an art form, as Miklos can do a perfect Mickey Mouse impression, and looks just like him with grey fur (hence the nickname):
      • In his debut in "Mickey's Dangerous Double" the police gets the both of them and promptly enlists Pluto, only to find him out of commission due his crush on a mannequin dog. They quickly asks Minnie, who first tells the right one (that the reader can recognize from the clothes) but then changes her mind. Numerous other attempts follow (including one relying on Mickey loving a cake that give a stomachache to everyone else that should have worked, except O'Hara got them the wrong cake, resulting in a double stomachache) until they end in a rainwater tank, at which point the Grey Mouse is unmasked thanks to him using washable dye;
      • In "Mickey Mouse and the Grey Scourge", Mickey's friends are enlisted to try and spot the right one but they fail (with Minnie once again getting the real Mickey but getting convinced by Clarabelle it was the other), and are on the verge of a fight when Casey shows up with Pluto, who this time is not out of commission;
      • In the 2014 story "Mickey Mouse and the Seven Boglins" Miklos has a more complex plan than usual, and for a while even Mickey is convinced of being the imposter (it helped he had been duped into taking fake vitamin pills that dyed his fur red and kept him unable to think straight), with the reader not being informed of which one is the fake until Minnie, once again, realizes the switch. This time, however, spotting the imposter is easy, as Minnie (who has evidently learned from the previous encounters) has tricked the fake into getting a tattoo and when comes the time to tell the right one she's quick to ask which one has it.
    • In the Disney Ducks Comic Universe this trope usually involves Paperinik stories, as he is a Master of Disguise and some of his opponents are just as good-or, in one case, better:
  • The Maze Agency: In "Two Wrong Rhodes", three women come forward all claiming to be lost heir to a fortune, and Jen and Gabe have to work out which one is genuine.
  • Mr. Natural, set upon by a horde of admirers, ducks into a store and emerges in disguise in a garish costume change - then encounters someone looking exactly the same, a guru named Holy Ned, who accuses him of stealing his look. Then three or four more identical guys show up. As they argue, Flakey Foont shows up, looking for Mr. Natural to give him money he owes him, and they all excitedly claim to be him. As they all stand identical in a row, a caption asks the reader "Which one is the real Mr. Natural?" Answer: none of them! He'd taken off to put the moves on the local hippie girls.
  • Power Pack: in "X-Men and Power Pack #2" of the all-ages series, Mystique impersonates Jack Power in order to escape the heroes. At Beast's suggestion that Mystique can only mimic a person's appearance but not their powers, Katie fires a salvo of energy balls at both Jacks, forcing the real Jack to assume his cloud form in defence while Mystique remains the same.
  • When she is in someone else's form, Mystique's eyes usually flare yellow when she is tired, excited, angry, or about to shapeshift again.
    • While she can copy someone's appearance, Mystique can't replicate powers. Thus, all it takes is seeing, say, Cyclops not firing eye beams or Kitty Pryde not phasing to realize who this is.
    • Depending on the Writer, Wolverine (or others with heightened senses) can sniff out Mystique but other times, they'll be caught off-guard. Likewise, sometimes son Nightcrawler and foster daughter Rogue are able to somehow tell it's her but other times can be fooled like everyone else. Perhaps justified as occasionally, Mystique lets them tell in order to get close.
    • Mystique used the "Shoot us both!" move when she and the SWAT team commander she was imitating were surrounded by SWAT officers; the cops obeyed, one fell, the other didn't; when a cop asked "Why are you still standing, sir?", "he" replied, ("His" eyes flaring yellow) !I just moved my vital organs into my lower body.....".
  • Even without Mystique, this happens a few times to X-Men:
    • Several of the team are at a beachside cafe when Gambit comes up. Everyone is shocked when Rogue tackles him over a cliff but when they land, "Gambit" turns into a Skrull. Rogue brushes it off as, having been raised by Mystique, she can tell a shapechanger.
    • The X-Men are fighting the Starjammers who they think are being mind-controlled and thus holding back. Corsair blasts Storm and gloats that "these Earthers aren't so tough!" Storm immediately notes how odd a phrase that is as "Corsair was born on Earth and proud of it!" The X-Men realize these are really Skrulls and thus can cut loose.
    • Visiting the mansion, Banshee is in a hallway corner when Psylocke exits Xavier's personal study. Banshee is less thrown by her being in an off-limits area than how he was able to hide in the shadows five feet away from a ninja-trained telepath. This leads to the discovery almost all the X-Men have been replaced by the Phalanax.
    • More than once, Wolverine has suddenly sliced up what seems to be a normal person only to reveal it to be some sort of robot and saying "it didn't smell right."
  • Laff-A-Lympics: During a relay race in "The Meet at Mount Ono", the Great Fondoo creates duplicates of Huckleberry Hound so Quick Draw McGraw won't know who to pass his team's rod to. Quick Draw eventually figures out who the real Huck is by having them sing "Oh My Darling, Clementine". The real one is more off-key than the imposters.
  • Secret Invasion: Avenger Crusader (who is actually a Skrull who decided to live as a human super hero) is in the Avengers' commissary, with a plate of kiwi fruit, strawberries and pickles. Together, the combo approximated the taste of a favored Skrull fruit. He realizes the Avengers have been infiltrated by (other) Skrulls when he sees Hank Pym serve himself the same combo.
  • In one issue of Usagi Yojimbo Gen gets lost in a forest haunted by nine-tailed foxes and runs into Usagi, and suspects he's a fox when another Usagi shows up. After fighting them both for a bit he realizes they're both nine-tailed foxes and runs for it.
  • In a Richie Rich comic book story, Mr. Rich is replaced with an impostor, and when the real Mr. Rich stands beside his impostor, both claiming to be the real Mr. Rich, they are both tested by lighting up a pipe and smoking it. The real Mr. Rich does this without any problem, but the impostor ends up coughing when he inhales from the pipe.
  • Heading to rescue Steve Trevor from shapeshifting Durlans, Wonder Woman and Captain Atom know who they're dealing with. When they're separated, each is approached by a Durlan posing as the other but see through it fast. In Diana's case, she asks "Atom" if Captain Nate Adam was with Trevor, the Durlan confirming it...not knowing Nate is Captain Atom. In Atom's case, he's able to quickly see that "Diana's" lasso isn't glowing.
  • The Iznogoud story "Fairy Tale" sees the title character recruiting hapless apprentice fairy Blunderbell to transform him into Caliph Haroun el-Plassid so that he can replace the real Caliph as head of state. However, she transforms the sleeping Caliph into a copy of Iznogoud instead; the copy then wakes up and immediately gets into an argument, then a fistfight with the original over which of them is the real Iznogoud. Blunderbell tries to resolve things with another spell, but only succeeds in transforming both Iznogouds into copies of the Caliph - and then she turns one copy of the Caliph into two copies of Iznogoud!

    Comic Strips 
  • Dick Tracy has former actor Harley Naiv disfigured and given a surgery that turns his face into a malleable shape that can allow him to look like anyone. Taking on the name "Putty Puss," Naiv often faces Tracy but his impersonations can be spotted.
    • To get money, Putty Puss poses as Diet Smith (who's running for President) for a speech where he makes outlandish statements guaranteed to ruin his campaign. Tracy, however, is able to use his 2-way wrist computer to record "Diet's" voice and while Naiv does a great impression, it still doesn't match Diet's distinctive voice pattern.
    • Putty Puss tries to pass himself off as Tracy but Sam Catchem is able to catch it with one simple fact: "It'll be a snowy day in July before Dick Tracy wears anything but a checkered tie."
    • Another time, Tracy is able to prove it's him simply by waiting as Putty Puss can only hold his face together for an hour before it starts to "melt."
  • One week-long arc in Dilbert had the Pointy-Haired Boss abducted by aliens and replaced by a double. Everyone in the office immediately realizes this because the double is competent and possesses people skills. Due to the differences being good ones, they don't even try to save the real boss (who frees himself by accident when he teaches them Earth management techniques, causing the UFO to crash after the captain downsizes half the crew).

    Fairy Tales 
  • In "The Two Brothers", collected by The Brothers Grimm, two identical twin brothers (with matching Loyal Animal Companions) set out to seek their fortunes; one has no particular luck, while the other rescues a princess from a dragon and marries her. When the brothers are reunited at the end, they decide for a laugh to go together to the court and not tell anyone which is which. Even the princess can't tell the men apart, but she identifies her husband after taking a close look at their animal companions. (Her husband's animals are wearing neck decorations she gave them after they helped kill the dragon.)

    Fan Works 
  • In Seven Little Killers, Japan intends to shoot Canada for being one of the killers, but can't tell him apart from America; it winds up being a moot point since the gun isn't loaded, so he just flying tackles one of them into the river.
  • In PnF: Stolen Identity, Ferb is replaced by a double for some unexplained but evil purpose. Said double spends the rest of the story acting so unlike Ferb that Phineas eventually thinks he's lost his mind and becomes completely terrified of his beloved stepbrother...meaning he fails this trope for most of the story. Fortunately he eventually figures out which is the real Ferb and the pair escape, leaving the evil double with the invention he needed Phineas to build for a reason we're never told.
  • In Out of the Dead Land, this trope becomes a recurring plot element when evil robot duplicates begin attempting to replace the Avengers. Bucky is able to detect the robot-Sam impostor with his Super Senses and exploit the robots' lack of blood to test others whenever he gets paranoid or suspicious, but he does still get fooled by them at crucial times, most notably when Hydra shoots a Steve duplicate that was specially made to actually 'bleed' convincingly.
  • In Doppelgänger, the Dark Doppelgangers have red eyes, which can distinguish them from their normal counterparts. However, Prussia has red eyes as well, making him identical to his. New Zealand solves this by punching them both in the face, as the doppelgangers have a nigh instant healing factor.
  • In this My Little Pony: Friendship Is Magic fan comic, Shining Armor's put in this situation when Chrysalis changes into Cadance again. He asks Cadance to say Something Only They Would Say, which leads to an argument over Shining's obsession with a tabletop war game. When Chrysalis says that she loves that game, Shining grins at Cadance and says now he definitely doesn't know who to shoot, much to her horror.
  • Infinity Crisis: In Different Strokes, when the Earth-51 Deathstroke attacks the team, Diggle and Thea assume it's their Slade. However, Oliver says the fighting style is different and how he took this guy down with a move Slade himself taught Oliver. Felicity then shows video of how this Deathstroke is a few inches taller than Slade and his voice pattern doesn't match either.

    Films — Animation 
  • Sev Trek: Pus in Boots (an Australian CGI spoof of Star Trek: The Next Generation). The crew find themselves confronted with two Captain Pinchhards, one of them a shapeshifting alien. Lt. Barf wants to kill them both, as the alien would revert to its natural state when dead, while Beta tries "statistical probability" ("eeny-meeny-miny-mo") but Commander Piker suggests asking a question only the real Captain would know.
    Piker: Captain, what is my favorite trombone jazz number?
    Pinchhard: How the hell should I know?!
    Pinchhard 2: Beats me.
    Piker: I played it for you on your birthday! You loved it!
    Pinchhard: Oh please! I slept through the whole thing!
    Pinchhard 2: Here's a combadge, Number One. Call someone who cares!
  • Toy Story 2. When the toys realize they have two Buzz Lightyears, the real Buzz cleverly reveals his double's true identity by pressing the button that opens the double's bubble helmet. The double falls to the ground gasping for air, the same way the real Buzz did in the first movie. He clinches the identification by showing the toys the name "Andy" on the sole of his boot.
  • Madagascar: Escape 2 Africa: Alex is forced to play this game when Marty blends in to a crowd of hundreds of zebras that look and sound exactly like Marty.

    Films — Live-Action 
  • X-Men Film Series
    • X-Men has Mystique pulling that trick too. However, Wolverine can smell the difference between Mystique and Storm, so he doesn't fall for it. Later, Cyclops asks Wolverine to confirm he is the real thing:
      Wolverine: You're a dick.
      Cyclops: Okay.
    • In X2: X-Men United, the trope is averted when Stryker is able to recognize his "handiwork" on sight — it's enough to fool the soldiers, but somehow the Colonel can tell with one close-up look. Which actually isn't that surprising. Parents can tell the difference between identical twins even when others can't.
  • Done in The Island, with a twist: the impostor was the protagonist.
  • Darkman did the same thing. His cover was blown, however, when his skin started melting.
  • Clumsily handled in Futureworld, the deservedly forgotten sequel to Westworld. The first movie, competently scripted and directed by Michael Crichton, features an average man (Richard Benjamin) being stalked by a gunslinger robot (Yul Brynner) through a robot-filled theme park. The robots are just enough "off" from real humans to get on your nerves. The sequel dumps all the subtlety and make the robots "perfect" imitations of humans, so it can save on acting and direction cost and steal the plot of Invasion of the Body-Snatchers. Late in the film, the two humans escape into the theme park and the boss robot, instead of ordering his trustworthy minions after them, sends out their own robot duplicates! This bit of Plot Idiocy telegraphs the movie's Spot the Impostor ending so ludicrously you want to shout "Oh, come onnnn!" at the TV set.
  • In keeping with the love that Star Trek: The Original Series had for this trope, it gets used again in Star Trek VI: The Undiscovered Country, at the climax of Kirk and McCoy's escape from Rura Penthe. A shapeshifter impersonates Captain Kirk, but it is the real Kirk the Klingons want to shoot. A "Shoot him he's the one" argument ensued, with an element of Fridge Logic: the shapeshifter should have tried to save herself by switching back to her normal form. She still would have been shot, but there's no explanation for why she doesn't.
    • Fridge Logic kicks in. The real Kirk still had his leg shackles on. The Chameloid morphed down to a little girl and had slipped out of them earlier. If you look at their feet during the "Kirk on Kirk" fight, you can see only one wearing them.
  • In Duck Soup, when Rufus Firefly goes down to investigate, the Mirror Routine apparently goes off without a hitch, and then near the end, while Firefly and the disguised Chicolini are closely examining each other, Pinky disguised as Firefly comes into the doorway and blows their cover, and once Firefly sees the two impostors, Chicolini faces trial in Freedonia.
  • Face/Off features a face-switch between the protagonist and antagonist, which both use to fool those close to their enemy. Hero Sean Archer convinces his wife of his true identity with the story of their first kiss.
  • Terminator 2: Judgment Day: Page quote of Bluff the Impostor... and the closing fight scene where the shapeshifting Terminator has impersonated Sarah Connor, and John must work out which is the real one (which wants him alive) and the bad one (who wants him very very dead). He picks the good one.
    • In the extended version, they reveal how John was able to make the right choice: due to the freezing/smashing/recombining the T-1000 went through, its morphing is damaged and it ends up copying the appearance of materials it is in contact with. John looked down and noted that the fake Sarah had a corrugated metal pattern on its legs. In another version, the heat rising through the grating below has melted her legs in the pattern of the grate.
    • In Terminator Genisys, the T-1000 impersonates Kyle but when the real Kyle comes in, Sarah doesn't know who to trust. She shoots one in the foot to see the reaction and it's the T-1000.
  • Red Dawn (1984). One of the American guerilla fighters finds an U.S. Air Force officer who's been downed behind Soviet lines and asks "What's the capital of Texas?" When he replies "Austin" she replies that it's Houston and accuses him of being a Dirty Communist. Tanner replies that she's been watching too many movies. (Ironically Tanner gives the right answer, probably a Shout-Out to the incident with General Bradley at the Battle of the Bulge.)
  • Happens twice in The Assignment (1997) about a US naval officer called on to impersonate Carlos the Jackal. On the first occasion a terrorist who knows the real Carlos accidentally runs into the protagonist at London airport. Unfortunately the protagonist tries to bluff his way out by pretending to be Carlos, and when the terrorist responds, "I need to get a newspaper" realizes too late that it's a password to which he doesn't know the countersign. Later his CIA handler mentions a similar incident where he was forced to kill a man who didn't respond with the correct countersign, and later uses this story to tell the difference between the protagonist and the real Carlos when he comes across them fighting each other.
  • The blood test scene in The Thing (1982) qualifies. In fact, given the creature's ability to disguise itself, this is a constant theme of the entire film. If the blood test counts, so does any film of TV show that homages the blood test scene, such as The Faculty, with the drug test.
  • Invasion U.S.A. (1952). A Russkie disguised as an American soldier doesn't know who the Chicago Cubs are ("Cubs? A cub is a small animal, a bear..."). Lampshaded by Tom Servo.
    American soldier: Ever see the Cubs play?
    Servo as the impostor: Yeah, they won... No! Damn!
    • And later spoofed:
    American patrol: Who goes there?
    Crow, panicky: Uh, the Cubs! Studs Terkel! Saul Bellow! Oh, whatever, just shoot 'em!
  • The climax of The Adventures of Pluto Nash involves the title character's fight against his evil clone and both wearing the same outfit. Pluto tricked the clone's goons into shooting the clone.
  • Dragonball Evolution has this with Chi-Chi fighting against Mai shape-shifted into her. Goku fails to spot the imposter and punches out the real one, allowing Mai to escape.
  • Police Academy 6: City Under Siege ends with the Big Bad posing as Commissioner Henry Hurst. To see who the fake one is, the police officers use the Pinocchio-test (they perform a nose pull on both commissioners, revealing the fake one is wearing a rubber mask).
  • In Muppets Most Wanted, Miss Piggy manages to tell Kermit and Constantine apart by asking both of them if they'll marry her. Constantine just says yes while Kermit stammers in his answer, making Piggy realize that the latter is the real Kermit.
  • In Enemy, Anthony's wife suspects briefly that Adam isn't her husband, but dismisses it. Adam's girlfriend, meanwhile, realizes who Anthony is leading to both of their deaths.
  • In John Carter, an enemy shape-shifter turns into John and fools Tars Tarkus at first. When the real John arrives, Tarkus is confused at first but makes the right decision when he sees red blood dripping from John's wounds.
  • The film version of Slaughterhouse-Five begins in World War II where soldier Billy Pilgrim wanders lost in the forest, and gets tackled by two American soldiers who think he's a German - they ask him who won the 1939 World Series. He doesn't know, and it turns out the other two don't know themselves.
  • Ice Cold in Alex. The Main Characters begin to suspect that the South African officer who hitched a lift with them may be a German spy because he doesn't know how to brew up a Spot of Tea in the preferred method used by South African soldiers.

  • The Alex Rider book Point Blanc ends with a genuinely disturbing sequence in which Alex and a clone of the BigBad surgically altered to look exactly like Alex go mano a mano. The prose deliberately acts like a distant camera, leaving the reader to play Spot The Doppelgänger and find it impossible, even when one falls into an inferno. In the next book, everything's all fine and dandy with Alex being the survivor, but...
    • Pops up again in Scorpia Rising: the clone (who survived the fall) and Alex are pointing guns at each other, and a CIA agent who comes on scene has to determine which of them just tried to assassinate the American secretary of state. He makes a correct deduction (Alex had a pistol, but the clone had a rifle, a sniper's weapon) but is shot before he can fire his own gun.
  • In the Thursday Next book First Among Sequels, Thursday fights off a fictional duplicate of herself. As a twist the writing changes so that we see things from the duplicate's point of view, despite being in the first person narrative, and without warning. It can take a reader a while to notice the switch.
  • Meg must perform this task in Madeleine L'Engle's A Wind in the Door, distinguishing her detested principal Mr. Jenkins from two imposters created by echthroi (which are essentially that universe's equivalent of demons). The imposters try too hard to be Mr. Jenkins and so fail, while the real Mr. Jenkins simply acts like himself (bored, confused, and wondering when this little game will be over).
  • Averted in Brothers in Arms by Lois McMaster Bujold. Miles is kidnapped, replaced by his clone, and interrogated; at one point in the interrogation, he and the clone are briefly alone together. He considers trying to trick his captors into thinking that he's the clone, but rejects the idea when he realizes that he hasn't shaved since he was taken and is currently sporting several days more stubble than the clone is.
  • The Iron Man novel Operation: A.I.M. had several Avengers battling shapeshifting "adaptoids"; Iron Man tricks the War Machine impostor into giving himself away by pretending his Powered Armor had a chameleon circuit. When the android uses this as an excuse to shapeshift in front of the others, his cover is blown two of the three other heroes there, Captain America and the Black Panther, were also adaptoids. Iron Man was at that point on his own but hadn't realized it yet. Later, the heroes must fight their own doppelgangers and resort to uncharacteristic tactics to win since the fakes know all their usual moves.
  • In the online novel John Dies at the End, determining who is a copy is simple, since their makers actually mark each clone's big toe. This leads to a Tomato in the Mirror for one of the Main Characters.
  • Subverted in Maximum Ride. After the situation is set up, the imposter is instantly identified by Angel, who points out "I can read minds, you moron."
  • Animorphs:
    • In the David trilogy, David morphs Jake's cousin, who is badly injured after being hit by a car and expected to die in surgery, and takes his place. Jake figures it out almost instantly, when "Saddler's" injuries are miraculously healed. Everyone else not in on the masquerade fails miserably.
    • David also impersonates Marco. When a Marco shows up, he's tested by the others: they make comments to him and see if he responds sarcastically.
    • A one-man variation in #6 when Jake gets infested by a Yeerk. The Yeerk is unable to contain its hatred of Andalites, and blows its cover for good when it protests being tied up for three days (the maximum duration Yeerks can survive without soaking up Kandrona rays), which the real Jake would instantly have agreed to.
  • It also gets some time in the Harry Potter books because of the Polyjuice Potion: at the start of Order of the Phoenix, where Lupin asks Harry what his Patronus is, several uses after the Seven Potters escape, and a number for trying to detect Death Eater impersonators.
  • Clive Cussler is fond of this in several of his books. Indeed the Dirk Pitt novel Iceberg has several examples:
    • Pitt is recovering from a plane crash in Iceland with a local doctor when a pair of cops stop by to ask questions. They state they just had coffee with the sergeant of a local village before he went on patrol. In private, the doctor tells Pitt the men are imposters as that sergeant doesn't patrol the area and is allergic to coffee. Pitt had already noticed one of the "cops" had patches on his shoulders where a sergeant's stripes would be.
    • Pitt meets with Kristi Frye, the long-hidden sister of the late explorer/researcher Kristjan Frye. Pitt is stunned when later in the book, it's revealed that Kristi is Kristjan, having undergone a sex change to be the woman she's also longed to be. While he didn't expect that, Pitt does find something off and over dinner, talks of how, in New Guinea, he ordered an echidna seaweed and Kristi agrees it's a great dish. An odd reaction given how Pitt just said he had the equivalent of "a New York cut steak wrapped in porcupine quills."
    • Asked how he knew something was wrong, Pitt explains that Kristi's tan was far too shallow for someone who was supposed to have spent years living in the South American jungle.
    • In the novel's climax, Pitt rescues a pair of diplomats from assassins on the Pirates of the Caribbean ride at Disneyland. Asked how he knew the killers were posing as robot pirates, Pitt quotes Walt Disney himself on "we were eyeball to eyeball and I saw the other fella blink."
  • Goosebumps:
    • Stay Out of the Basement involves a plant clone. After the clone is revealed to be a plant being, the plot seems to wrap up... until a flower in the front garden attempts to convince the protagonist that it is the real one.
    • In I Am Your Evil Twin, the protagonist uses his food allergy to prove that he's not the evil clone. Unfortunately, the clone swaps the target food for a version the protagonist is not allergic to, and then vomits on purpose, successfully fooling everyone into thinking he's the real thing.
  • Spoofed in The Culture novel Matter when Upper-Class Twit Prince Ferbin is on the run and seeks help from a former tutor who, to verify his identity, asks him a series of questions from his studies. When he gets them all wrong, the tutor responds dryly that Ferbin is indeed his indifferent student from long ago.
  • Played with in the Phule's Company book Phule me Twice, in which the identical looking robot is never recognised, despite its limited programmed responses, which are all casino based. Even the Company smart folk don't get suspicious, when advised to try the slots or the all-night buffet. Instead, they fear sunstroke. After Phules return, they use the robot to drive the unwanted new CO over the edge, as he wouldn't know about its existence.
  • In Sewer, Gas & Electric, Harry Gant is kidnapped and forced to compete against his robot duplicate in a video game, with his parents' lives as the stakes. His ex-wife breaks in to rescue the Gants, and the robot tries to trick her by voicing its "relief" at being "saved". She immediately shoots the robot, knowing that the real Harry is such a game addict that he wouldn't even notice her arrival.
  • God-Emperor of Dune inverts this, where there's an army of impostors and the task is to spot the real one. Leto II's Fish speaker army is facing a legion of shapeshifting Face Dancers who are impersonating his general, Duncan Idaho. When he scans the crowd, he immediately spots a naked one among the copies.
  • In a Nancy Drew book, when referring to a man who had been hospitalized, another man says, "taken to hospital", instead of "taken to the hospital". The former is a British term. The man has been posing as an American to escape crimes he was charged for in England.
  • Only resolved through a Deus ex Machina in Journey to the West when two identical monkeys claim to be the monkey king, and they take their fight to continuously more powerful divine beings, all of whom (except the last) fail to identify the real one.
  • Subverted in A Farewell to Arms by Ernest Hemingway. The protagonist (an American volunteer in the Italian army) is arrested as a German infiltrator because he speaks Italian with an accent — as does the military policeman arresting him, as most Italians were more familiar with their local dialect.
  • Partially subverted in the first story in Isaac Asimov's The Union Club Mysteries, where a club member named Griswold commented that spies sent to infiltrate defense agencies in particular were recruited from among people who'd spent several years in the US and were thoroughly grounded in American trivia. He then told of how he'd unmasked one such spy whom he'd been interrogating for hours by playing a word-association game which finished with him saying "terror of flight" and the spy responding "gloom of the grave." This was a giveaway because both phrases are from the third stanza of "The Star-Spangled Banner," and " loyal, true-blue American knows the words of the third stanza of our glorious national anthem" making it much more likely that it was a spy who had studied too hard.
  • In one of the Clue mystery series stories, Professor Plum makes several clones of Miss Peacock, alike in every way, save that the clone-Peacocks always lie. They corner all of them, all acting like fuss-budgets, all claiming to be the real Peacock, and the reader is asked how to tell them apart. The answer is to ask any simple question with a non-subjective answer, like "What is 2+2?".
  • Implied to happen offscreen in The Dresden Files, and rather frequently, at that. Ghost Story, covers how Chicago has gotten a great deal Darker and Edgier since the events of the previous book, Changes, six months previous. In order to verify a character's identity, Karrin Murphy demands him to "Bleed for me." Not only does he do so without protest, he has a pin on him for such a purpose. Harry notes that, while there are a great many supernatural shapeshifters, none of them can create convincing blood. He also comments on how bad things must have gotten in the six months he's been dead for the test to have gotten so commonplace.
  • The short story Granny Gumption Solves a Murder has the title character, a little old lady turned amateur sleuth, confronting the supposed returned son of a wealthy family. She knows he's the murderer who killed a doctor who was seeing through the ruse and says the tip-off was that his well-manicured hands don't match "the prodigal son who spent ten years working in the Peruvian mines," indicating he's an imposter. She urges him to turn himself in but he has other ideas.
  • Galaxy of Fear: The Nightmare Machine has an elaborate and convincing simulation going on in which the Main Characters' worst fears are realized. Zak realizes that his robot caretaker DV-9 is actually a sim because Deevee never reacted to the simulations before, among other things.
    • In Clones, the original and clone Hooles had fought a Shapeshifter Showdown; Tash had been watching, both because it was fascinating and because she didn't want to have to do this trope when they were done, but is interrupted and loses track. Soon she does have to spot which one is real... and comes up with something.
      "There's no way to tell you apart," she said, raising the blaster. "I'll just have to shoot you both."
      • The clone jumps at her, so she blasts him. The real Hoole asks how she knew.
      Tash shrugged. "Clones don't really understand feelings that well. The real Hoole would have known I couldn't shoot him, but the clone wouldn't know that. I knew he would believe my threat, and try to stop me."
      • Earlier in that book a clone of Zak wants Tash to enter a code, but she stops warily, thinking that he's supposed to know the code too, and why wouldn't he have done it himself? These clones have many of the same memories as their templates, but apparently in less detail.
  • In the story "The Brain Stealers of Mars", the thushol are Martian shapeshifting parasites who impersonate the heroes. They're also mind-readers, so that a duplicate has all the knowledge of the original, and the heroes can't find out who is the real one by questioning each other.
  • In the early story Counterfeit, an alien imposter who has infiltrated the crew is detected in a medical check because the imitation isn't quite perfect; amongst other faults, the alien has a blood-glucose level of zero — a real human would be dead.
  • In the Star Trek: The Next Generation novel "Rogue Saucer", Picard and his bridge crew, flying the stardrive section of the Enterprise, are confronted by two saucers — the Enterprise's own, and the rogue of the title. Picard and Worf quickly work out the solution: open fire on both. The one that fires back is the rogue.
  • The point of the story in Emily the Strange: Stranger and Stranger. The two Emilys are trying to determine which one is the real one.
  • The plot of The Tightrope Men by Desmond Bagley involves a man who has been altered by plastic surgery to resemble a Kidnapped Scientist. He gets a nasty shock when the man's daughter turns up for an unexpected visit, but is able to bluff things out for a while with the help of his government minders, until the day she informs him that she just spend the past hour testing him with a Long List of trick questions because she's tumbled to the fact that he's an imposter.


    Myths and Religion 
  • The Bible makes this Older Than Feudalism. King Solomon was famous for his wisdom, not only because he prayed for it, but because he was able to figure out which of two women was the mother of a child (a trope of its own). One woman's baby boy was dead, and both women claimed to be the mother of the living baby. He spotted the imposter when he offered to take a sword and cut the baby in half, allowing each woman to have a half of the child. The woman who protested that decision by giving up her claim on the child was judged to be the true mother. 1 Kings 3:16-28
    • Also, likely the origin of the "kill both of us" gambit, though that is a variation.


    Pro Wrestling 
  • The infamous nWo Sting angle in WCW where the nWo introduced an impostor Sting around the same time the real Sting had changed his look, meaning no one recognized him at first.
  • The infamous Dragon Door Project, whose main angle revolved around a half dozen wrestlers impersonating Ultimo Dragon or Tiger Mask, along with a Tiger Dragon.

  • During the "Pikachu!" number in Pokémon Live!, Jessie and James are hampered when multiple Pikachu appear, forcing them to pick out Ash's from a crowd.

    Video Games 
  • The Spy in Team Fortress 2 turns every game into one of these. You can't really be sure if that guy on your team is actually on your team, or if he's just waiting to stick a knife in your guts.
    • Or more likely, it turns every game into a case of "Kill 'em all, let the friendly fire system sort it out!" But servers with friendly fire enabled do play this trope straight, breaking spies in the process.
  • Spoofed in the last dungeon in Paper Mario, where a series of duplighosts (ghosts that can duplicate your partner's (and sometimes your) appearance and abilities) which "duplicate" your partner. The first two encounters are played more-or-less straight, but in the third, the three duplighosts trying to duplicate Kooper the Koopa end up looking and talking like several different characters, including Luigi, while still claiming to be Kooper. The one that impersonates Luigi even claims that you should trust him to be the real Kooper because you should trust your brother.
    • Done again in Super Paper Mario, where Mimi impersonates Merlee. You go through a dating game imitation to determine which one is the real one. The real way you tell them apart is by the fly hanging around the real Merlee - she was hiding in a toilet just before this incident.
      • It's also possible to tell by the way they speak - Merlee's rhymes and rhythm are perfect, but Mimi's are subtly inconsistent.
      • Also because Mimi's rhymes are about nasty and evil things.
  • In King's Quest VII: The Princeless Bride, near the end, the impostor king and real king fight each other as the hero stands by with a wand which can change the impostor back to his true form.
  • In Viewtiful Joe 2, right after defeating Frost Tiger, Joe finds two Sylvias, both claiming that the other is an impostor after the Rainbow Oscars. Being an Idiot Hero, Joe falls for the feminine wiles of the android impostor, even after Sylvia names the food they had on their first date.
  • In Granblue Fantasy, a chapter in the "Detective Barawa: The Jewel Resort Incident" event requires the player to choose who the imposter is among the 3 NPCs... by hitting them with their weapon. Chat Noir disguises himself as Therese in a bunny outfit.
  • At one point in Hamtaro: Ham-Ham Heartbreak, Spat first masquerades as Pashmina and coldly rips Penelope's blanket, then masquerades as Penelope and jumps all over Pashmina's scarf, causing Penelope and Pashmina to each think the other one is angry with them. Eventually, Spat settles on masquerading as Pashmina. How does this predicament get solved? The same way Solomon solved the riddle of the two mothers: Hamtaro and Bijou propose that both Pashminas tug really hard on Penelope...which hurts Penelope, so the real Pashmina is the one who lets go first to stop hurting her.
  • Tales of Symphonia: Dawn of the New World. Done when Emil comes upon two Lloyds fighting each other. Even if you never played the original, it's still pretty easy to figure out which one is the Lloyd responsible for all the atrocities in the world — he's the one spouting the cliched lines about justice and bouncing on the balls of his feet with a real-life ":D" expression.
    • This is actually easier if you've played the original Tales of Symphonia, since you'll remember that Lloyd hates cheesy cliches about justice.
  • Averted in Fire Emblem: Radiant Dawn. Pelleas, the alleged son of King Ashnard, hardly resembles Ashnard's real son at all, except for a mark on his forehead. In fact, the identity of Ashnard's real son is essentially irrelevant to the story.
  • In Metal Gear Ac!d, Teliko gets doubled by La Clown and they have a game of this with Snake. Her cover is only blown when the game begins again and the player (controlling both Snake and Teliko) gets a turn as Teliko.
  • There's also one in Metal Gear Solid Mobile, when Snake starts receiving Codec calls from a mysterious figure. This figure later claims to be Otacon. But Snake is being helped out by Otacon already, and he knows nothing about the other person — and can't even detect their Codec calls. It's later revealed the interloper is the real Otacon. The Otacon helping Snake is an AI based on Otacon's personality in the hellish VR simulation Snake has been put into.
  • In the fourth episode of Strong Bad's Cool Game for Attractive People, "Dangeresque 3: The Criminal Projective", Dangeresque is forced to choose between shooting his partner Dangeresque Too or the criminal lookalike Uzi Bazooka. Whichever you pick as the player, though, Uzi Bazooka is the one who gets shot.
  • Live A Live has the player stuck in the "Prove yourself" half of this in Cube's chapter. When faced with both Cube and a hostile robot modeled after him, Kato muses aloud that since the fake was only activated a short time ago, he couldn't have heard Kato's first idea for Cube's name (Koro or Rover, depending on your translation; either way, it's a cliche dog name). When you give the right answer, Kato yells for Darth to shoot the other one.
  • In Animal Crossing: New Leaf, on April Fool's Day, Blanca will arrive in your town, and visit a random neighbor. You have to guess who the real neighbor is; Choosing the actual neighbor instead of Blanca nets you a reward from your neighbor.
  • In Who is Mike?, the titular Mike comes face-to-face with a mysterious duplicate with the same memories and personality as him, and his girlfriend Sarah has to decide which one of them is the real Mike. There's also a story branch in which Mike has to choose between two Sarahs after the fake Mike impersonates her.
  • The final level of Fear Effect 2: Retro Helix has Hana being forced to identify which is Rain and which is Mist, with the choice determining the ending to the game. It's the one holding the disk — Rain's left handed.
  • A variant happens in Hyperdimension Neptunia Re;Birth1. Financier knows which identical copy of Blanc is the real one, but has to publicly prove it so Blanc gets her shares back. Her solution is to bring both Blancs to the town square and quiz them on her fanfiction. One copy answers the questions perfectly. The other gets defensive, avoids giving straight answers, and then starts loudly swearing at everyone present. The people instantly recognize the genuine article's short fuse, colorful vocabulary, and embarrassing hobbies.
  • In Treasure Planet: Battle at Procyon this happens in Mission 11, where the player encounters two ships claiming to be commanded by John Silver, and must work out which is the real one and shoot the imposter.
  • In Detroit: Become Human near the end of the game, if Connor goes to the CyberLife Tower and attempts to activate the androids in the warehouse, another Connor will appear, holding Hank hostage. A tense standoff will occur where the two fight and Connor must convince Hank he is the real Connor, after Hank aims at them both. Hank tell the Connors to tell him his dog's and son's name. Since Evil!Connor has all of Connor's memories, he isn't looking for the correct answer but the more empathic one.

    Web Animation 

    Web Comics 

    Web Original 
  • An early episode of The Series has a Shout-Out to the Red Dwarf example above, when the crew pick the real Doctor What from his Mirror Universe Evil Counterpart by rapid-firing questions about Paris Hilton at him. Later referenced when a different Evil Counterpart's deputy tries to use it, but the real Doctor What quickly shouts out the "right" answer and thus she picks the wrong one.
  • This video from an obscure YouTube channel combine this trope with both Take That! and Overly Long Gag.
  • Whateley Universe story "Test Tube Babies": Flying Brick Lancer fights power mimic Duplikat. Shroud finds herself facing two identical Lancers. One even tells her to shoot both of them to be sure. The team has a secret comm system so Shroud knows which one is the real Lancer.
  • In 80's Dan, Mr. Crabtree wanted to shoot whoever was the fake Dolly (even though the fake looked nothing like the real Dolly, and was a guy), not because the fake Dolly was dangerous, but because Mr. Crabtree just needed to let off some of his stress.
  • CollegeHumor:
    1. If you shoot the one with the green shirt, both the remaining guy AND the girl are revealed to be aliens.
    2. If you shoot the one with the yellow shirt, you killed the alien impostor.
    3. And if you shoot neither, the woman instead suggests a threesome between herself, her husband, and the alien clone, which is then revealed to be just a nightmare that the real husband was having.
    They left out the obvious fourth option — shooting both of them.note 
  • Parodied by Nigahiga when Ryan has his Evil Twin and one of his friends at gunpoint...and can't figure out who the real Ryan is.
  • Taken to the next level by Karl on The Ricky Gervais Show, whose stupidity was such that he did not like the idea of having a clone on the basis that he wouldn't know which one he was.
  • In the SuperMarioLogan episode, "Jeffy Sneaks Out!", Mario grounds Jeffy from going to the movies with Bowser Junior for repeatedly saying the F word, so Jeffy creates a clone of him from his Play-Doh (It Makes Sense in Context) to take his place while he sneaks out. Play-Doh Jeffy causes havoc at Mario's house, and towards the end of the episode, the real Jeffy gets into a fight with Play-Doh Jeffy, and Mario gets a hold of officer Brooklyn T. Guy's gun, with intent to shoot the Jeffy impostor. Despite the two Jeffys looking nothing alike, Mario and Rosalina are unable to tell them apart. At first, Mario sings "The Bunny Do", but both Jeffys dance along to it. He then grounds both Jeffys, and the real Jeffy goes into a swearing fit, prompting Mario to shoot Play-Doh Jeffy.

    Western Animation 
  • Zig-zagged in the Danger Mouse episode "Penfold Transformed." DM has two Penfolds on his hands—a robot duplicate planted with him by evil Dr. Augustus Crumhorn and Baron Greenback's henchman Stiletto Mafioso in a Penfold suit. The real Penfold was kidnapped by Crumhorn, but he managed to escape and be reunited with DM after the robot—having been turned into a mechanoid designed to destroy our hero—is destroyed itself.
  • Happened in a third-season episode of Gargoyles. Proteus is disguised as Elisa, and Goliath asks them both if Elisa ever doubted him, even for a second. One Elisa claims that she would never doubt him... and that's the clue that proves to Goliath that the speaker is not Elisa.
  • One episode of Johnny Bravo has Johnny have to figure out which is his real mother, between her and an obviously robotic duplicate. Of course, being Johnny, he picks "the shiny one", though when the robot duplicate tries to terminate Johnny's mom, he pulls out its battery pack, stating that his real mom would never hurt another living thing, not even a robot (right after she just got in a stylized fight scene with said robot, and right before she starts smashing it with a hammer.)
  • Foster's Home for Imaginary Friends, "Bloo's Brothers": After trimming a bunch of impostors down to 2, Mac ID's his Bloo after the remaining impostor goes on and on about how much memories they've (supposedly) shared together.
    Sappy Bloo: Mac, look me in the eyes, you know it's me. Think of all the good times we had together. The bond that we share, that only best friends can. Mac, you complete me. I-I love you.
    Mac: Okay, sappy, it's definitely not you. (points at other Bloo) You're the real Bloo.
    Bloo: Yes!
  • Codename: Kids Next Door:
    • "Operation: P.R.E.S.I.D.E.N.T.": The 4th Grade President and a robot replica thereof fight on a bus on its way to the City Hall (the real pres wants to cut down on school hours). One of them gets thrown off. Nigel stops at a city dump to slag the fake with an electromagnet and car crusher, while Hoagie takes the thrown-off real president to the Hall himself... except that the actual president was turned to his side by recurring villain Father, and school hours end up being extended to 8:25pm. In short, it didn't matter who got to City Hall Father was guaranteed to win.
    • "Operation: P.O.O.L.": Numbuh Four was clueless at first about Negative Numbuh One and Eizzil who were posing as Lizzie and the true Numbuh One; but, when the other members of the DNK showed up, he could tell that Negative Numbuh Three wasn't the real deal simply by looking at her. (As he told the imposter, "It's called being a friend!" Of course, his reasons likely went gone beyond simple friendship...)
  • X-Men:
    • Subverted when Morph, a shapeshifter, attacks Wolverine, shifting into his form. Jubilee, who can fire energy blasts, enters as they're circling each other. One Wolverine tells her to shoot them both, so she shoots the other one. However, the first Wolverine is actually Morph, who flees. Jubilee says that she figured only the true Wolverine would say that, while Wolverine remarks that Morph had the same idea.
    • When Bishop comes across Mystique disguised as Gambit and Gambit himself Mystique tries to convince him that she's the real Gambit, but Bishop who hates Gambit anyway, simply plans on blasting them both without prompting, but he's stopped by Rogue. Granted there was the simple way of only the real Gambit being able to use his powers anyway, but again, Bishop didn't like him enough to try.
  • South Park did the same thing, with the real (evil) Cartman correctly guessing that the "Shoot both of us" ploy would fool the others (who wanted to keep the "impostor").
  • The Simpsons:
    • Subverted in "Treehouse of Horror XIII"; when an army of marauding Homer-clones attack, Marge stops them by leading them into a canyon. She returns to Homer, but finds out the one that survived was actually a clone; however, he starts giving her a backrub, and she decides she doesn't mind too much.
    • In a non-THOH ep., Homer becomes a local Krusty "helper" (i.e. dons the makeup and costume so as to look identical to the original for local publicity), but the original Krusty is in trouble with the Mob. Both end up cornered at gunpoint in an Abandoned Warehouse, where the villains are initially flummoxed as to which one to shoot (which partly lampshades the show's limited animation character styles as both Homer and Krusty share the exact same basic frame, as well as both being voiced by Dan Castellaneta, which Groening actually intended so as to create a dynamic where Bart hated Homer but worshiped a man who looked just like him in the original shorts, and one of the early shorts story ideas was the revelation that Homer was Krusty), until Homer blows their cover by addressing Krusty by name. This being comedy, they survive anyway. Despite the limited animation character style, it actually was quite easy to tell the two apart - Krusty has a tuft of green hair on the top of his head, Homer two single hairs combed over it.
  • Family Guy:
    • Played with during a Flashback when Peter defeated his "evil twin". Lois has to pick one to shoot, shoots one, and while she and Peter are hugging, his face flips down showing he's a robot.
    • Parodied in the episode "German Guy", where Chris befriends an elderly puppeteer, Franz Gutentag but discovers that he used to be a Nazi. When Franz finds out, he takes Chris and Peter hostage; Peter knocks the gun out of his hand, and Chris grabs it, but suddenly he's confused which one to shoot. This is despite the fact that they look nothing alike, as Peter points out. Chris asks when is his birthday; Peter doesn't know, but Franz does, so Chris ends up shooting Peter in the shoulder.
    • A straight example in the next episode "The Hand that Rocks the Wheelchair", where Stewie creates an evil (or more evil) clone of himself, and Brian ends up pointing a gun at them; he lampshades the situation saying "Oh, come on, not this thing, really?" He eventually asks them to look at their feet, and shoots the one who doesn't start to laugh, as the real Stewie told him earlier that he spent an hour laughing at his feet. Unfortunately the Ambiguous Clone Ending suggests that Brian shot the wrong Stewie; it also helps that said ending is a Shout-Out to Michael Jackson's Music video of "Thriller".
    • This is also lampshaded at the end of "Thanksgiving", in which the "real" Kevin Swanson suddenly appears and tries to warn about the imposter in the room. "Wait! That man's an imposter; I'm the real Kevin Swanson!" Peter then remarks "Guys I don't think we have time for this." right before the episode ends (Conclusion: there was No Ending).
  • Danny Phantom: Danny gets accidentally body-switched with a ghost and proves his identity by telling Sam about the time Tucker threw up in her lunchbox back in elementary school.
  • The Transformers:
    • The Decepticons built a fake Optimus Prime that was remote-controlled by Megatron. However, the fact that he was so unfamiliar with the Autobots themselves almost blew his cover right away. He called them by the wrong names (like addressing Ironhide as "Bumblebee") and acted like he barely knew them, causing them to quickly become suspicious. When the real Prime showed up, The Autobots came up with some really stupid tests (one of them was to have a race) and when they didn't work, Megatron tried to have the imposter gain their trust by creating a clone of Starscream and having the Prime clone kill it (knowing that an imposter likely wouldn't turn on the Decepticons' second-in-command. It almost worked... But Megatron proceeded to expose himself by not being particularly worried about where their human buddy Spike had disappeared off to (being a little too eager to lead the Autobots to their doom).
    • Another episode had some of the Autobots disguising themselves as the Stunticons, a group of car-based Decepticons. This in itself is already fairly impressive, since almost none of the Autobots in robot mode have physiques resembling the Decepticon they're copying. The Stunticons naturally manage to escape, leading to a situation where two teams of Stunticons have to oppose each other, culminating with both the real and fake Stunticons merging to form Menasor, with a little help from electromagnets and hologram devices in the case of the Autobots.
  • In The Pirates of Dark Water, Bloth and Konk swap bodies with Ren and Niddler, respectively, using a potion concocted by Morpho, as part of yet another of Bloth's plans to steal the Thirteen Treasures of Rule. They could be distinguished by any reflection, which would reveal who it really was... or by which one did or didn't abandon you to be eaten by piranhas.
  • Subverted in the SpongeBob SquarePants episode "Imitation Krabs", where SpongeBob can't distinguish between Mr. Krabs and Plankton's robotic replica of Krabs — despite the fact that one is clearly a robot, complete with Robospeak, though SpongeBob did get weirded out by the Robot's "Metal Pants." SpongeBob gives the two Krabs a series of questions he thinks only the real Mr. Krabs would know. The first two are generic questions that anyone who's been to the Krusty Krab can answer and Robot Krabs answers them both. The third question is one that is so complicated that even the real Krabs can't answer.
  • The Tick featured a classic episode playing up Spot the Impostor, where an evil tentacular alien makes a very bad clone of the Tick's sidekick Arthur to spy on him. When the real Arthur escapes and confronts the Tick, he becomes infuriated that the Tick can't tell which of them is real despite the fact that the clone is green in color, shuffles around like a zombie and can only say the phrase "I... Arthur" (to which the Tick replies "He's got a good argument there.").
  • In one episode of Dungeons & Dragons, Hank correctly works out that the Dungeon Master is an imposter when he gives the group a straight answer. Unfortunately he doesn't realize that the Dungeon Master who shows up after that is also an imposter.
  • Averted in an episode of Teenage Mutant Ninja Turtles (2003) involving a robotic Master Splinter. Hun begins to try this when the real Splinter shows up, only to be reprimanded by Shredder, who has already decided that they'll never fall for such an obvious trick.
  • In Jonny Quest: The Real Adventures, Jesse has two Jonnies at gunpoint in the "Questworld" virtual reality program. One starts reeling off the details of their last race in Questworld. The other Jonny counters that that's in the computer's memory banks, then brings up their real-life race immediately thereafter, which reveals him to be the real Jonny. The double attacks him, and gets zapped in about half a second by Jesse.
  • DTZ, from the Chip 'n Dale Rescue Rangers episode "Dale Beside Himself", wasn't really evil, he just didn't want to go home, so he took Dale's place and sent him off to Fleeblebrox. Dale manages to come back, but the Fleeblebroxians aren't leaving Earth without him. With the threat of planetary atomization hanging over his head, Dale gets the idea to retrieve a platter of erkburgles (single-eyed squid-blob things with green skin and red scleras)... DTZ's favorite food. Unable to resist, DTZ starts scarfing and is subsequently caught.
  • The eponymous clown in the Garfield and Friends episode "Binky Goes Bad!" is jailed and brought to trial for the crimes of a man who hated him, and who decided to dress and make himself up like him in order to commit crimes and have Binky take the fall. Stinky is eventually revealed as being the fake when Garfield gets the judge to say "Order in the court," and Binky quips "I'll have a ham on rye. Hold the mayo!". Stinky, not saying anything is exposed as a fraud, is sent off in the paddy wagon. Garfield notes the real Binky could never resist a very old joke.. Incidentally, Garfield is dismayed that he's in an evil twin episode.
  • This happens fairly frequently in Code Lyoko with the Polymorphic Clones.
    • The first occurrence is with XANA himself impersonating Jérémie in "Ghost Channel". (Basically, it is a case of Evil Cannot Comprehend Good; XANA insists that Jérémie is too afraid to ever come to Lyoko, but the others know that he will if their lives are in danger. XANA's ignorance of how Jérémie would react led the others to realize it is him.)
    • In "XANA's Kiss", when confronted with two Jérémies, Aelita can guess which one is genuine because the Clone had kissed her without permission, which the true Jérémie would not have dared to do. (Maybe XANA can comprehend good, just not very well...) Later in the same episode, Odd recognizes the real Yumi from the Clone impersonating her when the Clone doesn't insult him while the real Yumi calls him a pea-brain. (He knows it was her. Odd may be insulted a lot, but he knows that XANA would never call him a "pea-brain".)
    • Subverted in "Opening Act", when Jim Moralès can't tell apart his nephew from the Clone, and ends up dumbly attacking the real Chris.
    • Both time that X.A.N.A. pretends to be Franz Hopper, he gets caught by two different people. In "Franz Hopper", it's Jérémie realizing about lines on Franz's ruined dairy. (The real Franz would not have known that.) In "Distant Memory", it's Aelita who realizes what's going on when X.A.N.A. calls "Skidbladnir" a funny name and no virtual take for Aelita's mom.
    • Subverted in "Image Problem". The team is suspicious of Yumi's imposter, but no-one truly catch on until she actually becomes hostile. (Of course, it is the first time XANA has tried something like this.)
  • Darkwing Duck:
    • They use the split personality variant for the episode "Negaduck". When Gosalyn and Launchpad decide to set free the good Darkwing to help them retrieve the Applied Phlebotinum that caused the split, in order to undo it, they mistakenly release the evil Darkwing, and he pretends to be the good one briefly, until he can effect his getaway.
    • In subsequent episodes, the unsplit genuine Darkwing has an actual Evil Twin who goes by Negaduck, and on multiple occasions one of them has disguised himself as the other, resulting in Spot the Imposter scenes for the allies of whichever one they're disguised as. One memorable moment has Darkwing and Negaduck dressed identically (except Negaduck wears a black mask) and acting so much like each other that they mirror each other's words and body motions perfectly. Then Darkwing breaks the impasse by declaring that a cute defenseless bunny rabbit is nearby, whereupon Negaduck (who was hatched from a Villain Ball) compulsively tries to kill the bunny with a shotgun. Before that, however, we get this memorable solution:
      Dr. Bellum: [completely nonchalant] Well, we'll just have to kill them both. [arms bazooka]
    • Funnily enough, Darkwing tries the same ploy to infiltrate the Fearsome Five's HQ., using a Negaduck costume (minus his purple mask, again for audience benefit). He gets all the way up to the five — WHO HAVE JUST RESOLVED TO KILL NEGADUCK FOR SCREWING THEM OUT OF THEIR SHARE OF THE CITY'S LOOT.
      Darkwing Duck: Hey! What's the deal? IS THIS ANY WAY TO TREAT YOUR LEADER!?!? (So much for the 'perfect disguise!)
    • When Negaduck returns, it leads to one of the best Never Say "Die" aversions ever seen.
      Bushroot: Kill Negaduck! Kill Negaduck!
      Negaduck: [still reeling from Darkwing's anvil attack] Kill who?!
      Darkwing: No, wait, I'm DARKWING Duck; HE'S Negaduck! KILL HIM!!
      Negaduck: You thought he was me? You were going to kill... ME?!?!?
      Bushroot: No, no, no! We knew it was Darkwing! We were just testing, see?
      Quackerjack: Wait, didn't we already kill Darkwing Duck?
      Bushroot: Gah! THE GHOST OF DARKWING DUCK!!
      Liquidator: He's baaack!
      Negaduck: [beyond pissed] JUST... GET HIM NOW!!!!!!!
  • An episode of Duck Dodgers features an escaped criminal named Drake Darkstar who looks almost exactly like Dodgers. Dodgers tries to prove his identity to the police by appealing to the Cadet by listing things only he would know, but every single thing he lists is a mean prank he played on the Cadet. The Cadet ends up declaring Dodgers to be the criminal, reasoning that Darkstar would be nicer to him than Dodgers ever was.
  • Subverted in Stroker and Hoop when Hoop and his evil-identical-cousin are holding a gun on each other, with Stroker nearby. Stroker shoots one of the Hoops in the knee, causing the other one to exclaim "Good job, Stroker" before Stroker kneecaps him too. "Now we can figure out who's who at our leisure!" This being Stroker and Hoop, they still get it wrong (at least until they spot the evil one pursing his hands with an evil grin as they prepare to drive off)
    C.A.R.: We'd better double back and make sure.
  • In an episode of Where on Earth Is Carmen Sandiego?, Carmen's henchman Sarah Bellum attempts to take over Carmen's organization, and a big part of this is disguising herself as Carmen. After she captures Zack and Ivy along with the real Carmen, Ivy quickly figures out how to tell the two apart: Sarah is left-handed (because the controls on the vehicle she uses are on the left side) but the real Carmen is not (she tosses her a tool from her cell - with her right hand - that they use to escape). After they are separated from Carmen briefly and later have to decide who is who, Ivy simply throws it to one of them, and the fact that she catches it with her left hand is enough proof that it's Sarah. (As for why they decide to nab her and not Carmen, well, since Carmen helped them escape, they owed her one.)
  • Kim Possible: When confronted with a shape-shifted Camille Leon, Kim can quickly identify the real Ron, but when it is Ron's turn in another episode, he picks the wrong one, to Kim's annoyance. Kim had to rely on Camille being unable to duplicate Ron's ever-present pet, despite the fact that Camille stood in a pose that was obviously nothing like Ron's and utterly lacked Ron's Cloudcuckoolander personality. In the episode where Ron had to pick, Camille apparently worked on those flaws in her disguises, and Ron, having been trapped in a crate the entire episode, had stumbled onto the scene only moments earlier, and had absolutely no idea what was even going on. Even Monique, who had been touted as the one who got it right, wasn't actually able to distinguish between the two; she simply identified the disguised Camille's outfit as an expensive one more likely to be worn by spoiled heiress Camille than by the more practical Kim. note 
  • Jackie Chan Adventures: In an episode involving a group of Evil Knockoffs cloned off the Five-Man Band, Jackie's clone is found but the rest of the group needs to know which Jackie is the real one. Jade asks both Jackies if they can take her to an amusement park, the first says yes while the second says no and tells her to do her homework. Jade knows better and the first Jackie is exposed as the clone. In the same episode, Paco keeps calling Jade by pronouncing her name correctly, while in all the other episodes he pronounces it "Yade." She catches on to this as well and it is exposed that he too is a clone. Before Jade asked about the amusement park, Capt. Black made an attempt by asking about his birthday. Neither Jackie knew the day.
    Captain Black: Geez, Jackie, I thought we were pretty good friends.
  • Wild Kratts: A Zachbot disguises itself as Chris in order to convince Martin that everything's okay, as opposed to, say, locked in a cell and glaring at his impostor from off-screen. Martin gets it in the end though. Oddly, while Martin misses the fact that "Chris" is wearing red instead of his signature green, he does notice and react to "Chris" saying "Toodles" to close their conversation.
  • In Transformers Animated, in order to determine who is the real Bumblebee after Wasp switched their paint jobs, helmets, and voices synthesizers, Bulkhead has them play a video game that Bumblebee is the undisputed master of. Wasp takes Bumblebee hostage before his cover gets blown.
    • Now, before that point, the real Bumblebee mentioned covering for Bulkhead back in boot camp (something no one else knew), but Wasp, who had looked up on the Autobots' files while the rest of them had gone, rendered that unable to work when they all got back to their base. At the same time, however, Wasp had proved himself completely pathetic at the aforementioned video game, hence why he cracked.
  • Futurama:
    • The "Lesser of Two Evils" episode completely revolves around this trope, reaching the obvious climax when Bender and Flexo get into a Mirror Match. Leela has a laser gun but can't tell which to shoot, to which Fry unhelpfully remarks: "Flexo! Shoot Flexo!"
    • Subverted in yet another Mirror Match in "Rebirth", with Leela and her robot double fighting over Fry:
      Leela: Shoot her! She's the robot!
      Robot Leela: No! Shoot her! She's the human!
      Fry: B-But how will I know who's the human and who's the robot?
      Leela: We just told you!
      Robot Leela: Yeah, you idiot!
  • Robot Chicken:
    • Used to hilarious effect in a He-Man sketch. Skeletor commissions Beast Man to create a magical clone of He-Man. The result is the blue-skinned, incredibly stupid clone Faker. Undaunted, Skeletor sets Faker upon his enemies. Its odd appearance, mannerisms, and speech go unnoticed by all except Prince Adam himself; in fact, this laid back clone is far more popular and quickly becomes the life of the party, much to Skeletor's annoyance. When Adam returns as the real He-Man, Faker has either killed or captured most of his enemies. He-Man's outrage at the act, as well as the general hedonism Faker has inspired, leads the crowd to dub him a wet blanket and vote him as the imposter (even though Faker voted for him as the genuine article). He-Man is then executed, and it is only after Faker expresses no knowledge of being Prince Adam does someone finally catch on.
    • Subverted at the end of the "Michael Jackson vs. Michael Jackson" sketch.
      Alien 1: How were we going to take over the world with a white Michael Jackson anyway?
      Alien 2: Damn it! Damn it! Damn it!
  • Used in Action League Now on Nickelodeon. The villain has created a "perfect duplicate" of the heroic (if moronic) Flesh (who looks just like him except for the various bolts sticking out of every part of his body and his mechanically modulated voice). When the two Fleshes square off, the rest of the Action League try to determine which is the real one by asking for the League password. Both incorrectly guess "devilled egg". Finally Stinky Diver gets the idea to yell "Hey, stupid!", knowing only the real Flesh would respond.
  • Inverted in Chaotic (the cartoon based on the card game), when season Big Bad Aa'une goes One-Winged Angel, leaving Maxxor, Chaor, and Iparu hopelessly outclassed — until Iparu uses his copycat-shapeshifting power to mimic Aa'une's transformation and level the playing field! Chaor solves the inevitable who's-who dilemma by drawing attention to himself just before jumping off a cliff; Iparu instinctively saves him, and the good guys triple-team the real Aa'une.
  • In an episode of the Animated Adaptation of Richie Rich, an imposter impersonates Dollar, the dog. In an attempt to determine who is who, they present both dogs with a bowl of dog food. The imposter forces himself to eat it, and is promptly exposed. What he didn't realize was that the real Dollar is much too spoiled to eat common dog food.
  • Inspector Gadget once had to deal with this problem when Dr. Claw hired a Master of Disguise to impersonate him and spy at an important police conference. Gadget eventually confronts his evil lookalike, and no-one can figure out who's real and who's fake. Eventually, the real Gadget stands next to Chief Quimby, and his Gadget mallet activates on its own and bonks Quimby on the head. The dazed Chief immediately orders the police to arrest the other guy, since the one standing next to him is obviously the real Gadget.
  • Johnny Test has this when Johnny and Dukey encounter their cyborg clones. After disposing of his clone with a "Fetch the Grenade" trick, Dukey takes the Clone's weapon and confronts the Johnnys. The cyborg immediately does a Doppelgänger Spin so they can't tell which one's real and which one's the cyborg. Dukey eventually manages to get the cyborg to give himself away by asking a math question, and blasting the one who answers immediately, knowing that Johnny always does math by counting on his fingers.
  • One episode of Goof Troop has Goofy and a counterfeiter who looks just like him. Max identifies his father by leaving an open bucket of wallpaper glue in front of the two of them and asking his real dad to step forward. Both of them step forward, but only the real Goofy steps in the glue.
  • In the Fish Police episode "The Two Gils", Gil's nemesis Calamari hires a guy named Bill who looks just like Gil, training him to act like him so that the real Gil will be blamed for whatever crimes he commits. Eventually the two meet face to face and get into a fight. No one can tell the difference, so they try a series of tests; nothing works. Finally Gil gets the idea of showing his badge. The fake reveals he has nothing on it, (the real Gil's contains a living starfish named Sandy), and the fake is arrested.
  • In the Mister T animated series, kid sidekick Spike and his older sister are led to believe that their eldest sister, who Spike idolized, has turned up alive, years after she disappeared in an accident. The well-planned scam is undone by Spike, when, seeing the fake of his dead sister on-screen, hears her call him Spike and ask for his help—except that Spike was a nickname he only picked up after she was gone.
  • Subverted in G.I. Joe: Renegades when Zartan impersonates Duke. The Joes catch up and find the real Duke fighting the impostor, resorting to the usual Something Only They Would Say ploy by asking them a question about a conversation from the beginning of the episode. Duke doesn't remember it and they both say "no idea." Snake Eyes, who can hear the difference in their heartbeats, kicks Zartan in the face before it can escalate.
  • In Ozzy and Drix, Drix thinks up a rather unique way to do this when Ozzy is fighting his Evil Clone - he takes out his cellphone and dials the number for Ozzy's phone. The real Ozzy picks up the phone - Drix knew only the real one had it - and says, "Uh, I really can't talk right now!" And Drix replies, "That's okay, neither can I!" and then shoots the imposter.
  • One episode of Dog City has Bugsy Vile impersonating Barney Expy Bernie, the Big Pink Saint Bernard. At the end, the real Bernie appears and challenges his double to a sing-off of his Show Within a Show's theme song ('X is Good, X is Nice, X goes with everything, even with Rice', where X is something related to the theme of the episode). Halfway through verse three, Bugsy unmasks himself and begs the police to take him away.
  • On Regular Show a shapeshifting otter tries to take Rigby's place and the others can't tell them apart. Mordecai points at one of the Rigbys as the real one and asks for a hug. He does... which is how Mordecai knows he's the imposter, because the real Rigby hates to hug.
  • American Dad! did this when Francine realizes that Stan assigned Bill (his double) to keep herself company while he dates the prom queen. She gets furious and pulls out Stan's gun, but can't tell them apart. One of them steps up apologizing and loves her, but Francine assumes the other Stan is the real one and shoots him thinking that Stan will never say something like this. It turns out the apologizing Stan was the real one and Bill was the one shot.
  • Spider-Man: The Animated Series:
    • This happens in almost every episode that The Chameleon is in. When he tries it during a fight with Daredevil, Spidey had the requisite "I don't know which one to hit" moment — only for the genuine article to simply outfight Chameleon.
    • Then there is the time that Spider-Carnage kidnaps and replaced our Peter (who is himself pretending to be this reality's — long story — Peter). Gwen Stacy sees through them both, recognizes that our Peter is still the heroic one, and frees him.
      Peter: How did you know that the other Spider-Man wasn't me?
      Gwen Stacy: The one downstairs? He's as nutty as a fruitcake. A girlfriend notices these things.
  • Played with in the The Spectacular Spider-Man episode "Persona". The Chameleon dresses up as Spidey, framing him for various crimes. However, when Captain George Stacy sees the imposter in person, he notes that he's too tall to be the real thing. When the real webslinger shows up, he easily proves he's the real deal (despite his new costume) by overpowering Chameleon with his spider strength and agility.
  • Transformers Prime:
    • Bumblebee was able to figure out Nemesis Prime wasn't the real Optimus because Nemesis (and by extension MECH) couldn't understand Bumblebee's form of speech.
    • Another episode, introducing Wheeljack, has Bulkhead show misgivings about being with his fellow Wrecker. The Wheeljack that shows up is a shape-shifting body-copying Decepticon named Makeshift. Bulkhead forces 'Wheeljack' to tell a story about a battle, which Makeshift initially gets right... but he flubs one critically important detail, revealing the decepti(c)on.
  • My Little Pony: Friendship Is Magic:
    • Averted in the season 2 finale when Twilight Sparkle and the real Cadance crash the wedding that has Queen Chrysalis posing as Cadance. The villain gives up the pretense, concluding that since Twilight Sparkle's previous voiced suspicions about the bride now have the real Cadance's support, everyone else will instantly put one and one together and realize who is imposter is.
    • Played straight in the episode "Too Many Pinkie Pies". Pinkie used a mirror pond clone herself, but too many clones are made and Twilight needs to know which Pinkie is real or she might get rid of her by accident. So Twilight forces all the Pinkies to watch paint dry and sends anyone who gets distracted or stops looking back to the mirror pond that they came from, because the real Pinkie would do anything for her friends.
  • The Life and Times of Juniper Lee: Ray Ray has to identify the real Juniper. One failed attempt consists on asking both Junes to tell her middle name. Both knew it is "Kim". Ray Ray eventually manages to tell who the real is the same way Jade did with Jackie in an above example. To her dismay, he is helped by a zit she tried to rid herself of earlier.
  • Justice League:
    • In the multi-part episode "Secret Society", it was pretty easy for Batman to tell that the guy claiming to be Flash was actually Clayface in disguise. As Batman put it, the villain "overplayed your part". On another note, in the same multi-part episode, the villains were downright terrible at this. They didn't realize that J'onn J'onzz had disguised himself as Clayface until it was too late. Clearly, Grodd is a sorry excuse for a villainous mastermind.
    • In a later episode, Flash and Lex Luthor have switched bodies. After Doctor Fate switches them back, Green Lantern suggests testing to see if Flash is back in his old body. Flash responds by starting to reveal John's Embarrassing Nickname before he gets cut off. As for the villains, they apparently thought that Luthor was just a bit addled after his attempt to mind-probe Grodd. Grodd knew the truth, but kept mum — he hated both Flash and Luthor, and decided to watch his enemies' predicament unfold.
  • When Olive Oyl invites Popeye to eat hamburgers at her place, Wimpy disguises himself as Popeye and manages to fool Olive. Popeye then eats his spinach and defeated Wimpy. It's unclear if Popeye ever tells Olive it was Wimpy or that he actually fooled her.
  • The cartoon version of Punky Brewster had the episode "Double Your Punky." While Punky is at a school picnic, Glomer creates a clone of her from a photograph to keep him company. But this clone is obnoxious and she escapes. In his confusion, Glomer zaps the sweet Punky back into the photo and tosses it away. He retrieves it and brings her back but during a scuffle with the clone, nobody can tell who the real Punky is—nobody except her dog Brandon, who recognized her scent.
  • The Beatles cartoon episode "No Reply" dealt with a jewel thief who has disguised himself as Paul McCartney. What tips him off is that when the boys are confronted by screaming female fans, the thief doesn't run.
  • The Powerpuff Girls:
    • The Too Dumb to Live citizens of Townsville take three hardened criminals poorly disguised as the actual heroines in "Powerpuff Bluff." The real Powerpuffs get locked in jail.
      Ms. Bellum: Uh, sir, this might just be me, but don't you think the girls were acting a little strange?
      Mayor: How so?
      Ms. Bellum: Well — robbing the bank, the jewelry store, your house? Beating the living daylights out of you? Need I go on?
      Mayor: Yes, I'm not following.
      Ms. Bellum: The deep voices, the facial hair, the height! Not to mention the manly odor!
      Mayor: And? And?
      Ms. Bellum: Those were men dressed up as the Powerpuff Girls! Understand?
      Mayor: Yes! There's only one thing to do! [walks to the phone] Hello, Chief of Police? Arrest the Powerpuff Girls!
    Even worse, later when the girls and imposters confront each other even THEY can't tell the difference between the reals and fakes, resulting in them each hitting their own side.
    • "Him Diddle Riddle" poses a problem entailing two Miss Keanes, each bound and suspended over a tank of sharks. Him explains the real Miss Keane will tell the truth while the fake one will not and they can only ask one question. By asking them who they think the real Miss Keane is, Blossom figures it out. Though it also made for a pretty noticeable continuity error among fans of the series, as in spite of her reasoning being correct she still picked the wrong one..
  • Teamo Supremo:
    • In an episode, there's a villain named Madame Snake who's a master of disguise. Near the end of the episode, Madame Snake has disguised herself as Mrs. Woolingantz, our heroes' teacher, so the team has to figure out which one is the real teacher and which one is Madame Snake. Interestingly, while Mrs. Woolingantz is nice, Madame Snake is eventually caught when she tries to act too nice: Madame Snake promises not to give the team any more homework for the rest of the year. The team finds this tempting, but it proves she's the fake: the real Mrs. Woolingantz may not give a lot of homework, but she gets "really upset if you don't do it", so the real deal would never have made that kind of offer.
    • Madame Snake had actually been impersonating Mrs. Woolingantz the whole episode; she had replaced her so she could give the trio so much homework that they couldn't do any crimefighting. They eventually got a pardon from the governor for the evening which incidentally was the way they managed this trope: they brought up the pardon and Madame Snake responded as mentioned above while the real Mrs. Woolingantz was furious at the governor's giving her students the pardon.
  • Back at the Barnyard:
    • In "Doppelganger", at the vet's office, stray dog Baxter switches places with Duke and even spray-paints himself to look like him. The animals take him home instead of Duke. When the real Duke returns, none of the animals are able to tell them apart (even though they look nothing like each other, not to mention Baxter always gets everyone's names wrong), except for Otis, who knows that Pig's pet skunk, Skunky, absolutely loathes the real Duke.
    • In "A Tale of Two Snottys", Eugene (A.K.A. Snotty Boy) gets amnesia and the animals send Pig dressed in his clothes to the Beadys' house until they can restore Eugene's memory. When Eugene does get his memory back, Mrs. Beady is unable to tell them apart, even though they not only look nothing like each other, but are also dressed in different clothes, and have different personalities. However, the third difference is exposed when Pig saves Mr. Beady from a fallen ship in a bottle, as Mrs. Beady knows the real Eugene wouldn't risk his life to save her husband's.
  • In an episode of The Fairly OddParents!, Benedict Arnold disguised as George Washington nearly tricks John Hancock into signing a document called "The Declaration of Surrenderpendence". Timmy and the Founding Fathers show up, and the real George Washington stops Hancock before he can sign the document. When everyone is unable to tell Washington and Arnold apart, Timmy brings in a wooden coat rack and the real Washington chops it to pieces.
  • In the Tuff Puppy episode, "Bark to the Future", The Chameleon disguises himself as Dudley from the future. When he and the real Dudley get into a scuffle, The Chief orders Kitty to shoot the impostor. Kitty asks the two how Dudley spells his name and The Chameleon disguised as Dudley spells it correctly. Kitty shoots The Chameleon, because she knows the real Dudley can't spell his own name.
  • In the Static Shock episode "Toys in the Hood" (a cross-over with Superman), the Toyman creates a synthetic copy of Static's girlfriend Daisy, forcing Superman and Static to figure out which is which. The copy is such a perfect match that even with his x-ray vision Superman cannot tell the real Daisy from the fake one. Static solves the problem by making the electric aura that all humans have visible; the Daisy without an aura is the fake one.
  • In the Timon & Pumbaa episode, "I Don't Bolivia", Timon lets Toucan Dan out of a cage to help him break open a snail shell. Towards the end of the episode, in order to avoid being put back in the cage, Toucan Dan appears in an unconvincing Timon disguise. Even though Timon and the disguised Toucan Dan look nothing like each other, Pumbaa is unable to tell them apart, so he uses a test, in which only the real Toucan Dan can break open a snail shell.
  • Defied in Rick and Morty episode "Close Rick Counters of the Rick Kind", when the main characters are being chased by alternate universe versions of Rick. After chasing them into a restaurant, the Alternate Ricks ask the patrons to help them and draw red X's on their foreheads to prevent this situation from happening.
  • In the Gravity Falls episode "Into the Bunker," Dipper, Mabel, Wendy and Soos encounter a shapeshifting monster. It later takes the form of Wendy. Dipper figures out who the real Wendy is because the real Wendy zips her mouth, which is what she did before she entered the bunker to show Dipper to swear herself to secrecy about the bunker.
  • When Mark was cloned on Ugly Americans, Frank was forced to choose who the real one was. They two Marks were actually visually distinct, but Frank had been blinded in a fight with the Evil Twin earlier. Frank shoots them both in the leg, and calls for help from someone who can actually tell them apart.
  • A variation in The Flintstones episode "Rip Van Flintstone"; an elderly Fred wakes up from a 20-year nap and goes to Barney, who had since become a multimillionaire, but since several other people have come up to him claiming to be the long-lost Fred Flintstone, Barney manages to prove that Fred's the real deal by having him call for Dino, which causes the dinosaur to pounce his master and lick his face like always.
  • Parodied in the Dexter's Laboratory cartoon "Beard to be Feared" where Dexter gives himself a beard and suddenly nobody is able to tell the difference between him (a tiny Caucasian child with red hair) and Action Hank (a muscular African-American adult).
    Villain 1: Two Action Hanks?!
    Villain 2: But which one's the real one?
    Villain 1: Who cares?! Get them!
    • Subverted in "Momdark", where Mandark kidnaps Mom and disguises himself as her so that he can infiltrate Dexter's Lab and destroy it. But then Dexter, Dee Dee and Dad keep asking her to do chores so much that Mandark doesn't have any time or energy to destroy Dexter's lab. Then the real Mom breaks free of her captivity and shows up home, confusing the family before Dad suggests keeping them both.
  • In the Hero: 108 episode "Leech King", the titular character takes shape of Lin Chung and fights the real one, prompting Commander ApeTruly and the rest of First Squad to become confused as to which one is the real one (complete with ApeTruly asking "Lin Chung, is that you?" and both of them saying "Yes."). When Mighty Ray exclaims that he can't tell which is which, the real Lin Chung quickly settles the difference by telling him to blast both of them.
    Mighty Ray: Only the real Lin Chung would take an eyeball lightning blast for the team.
  • Kaeloo: In the episode "Let's Play Happy Rotter", Mr. Cat uses a magic spell to make himself look just like Quack Quack. Bad Kaeloo doesn't know who to beat up. She then remembers that by mentioning a certain detail from a book series, she can send the real Quack Quack into Troubled Fetal Position and identify the impostor.
  • He-Man and the Masters of the Universe (1983):
    • In "She-Demon of Phantos", Skeletor tricks Queen Elmora by casting illusions so He-Man looks exactly like him, making her unable to tell them apart. He-Man solves it by asking Elmora to use her magic to tie both of them up with Photanium chains. He-Man can break through them, while Skeletor can't.
    • In "Double Trouble", the Mirror of Moravad creates doubles of people with opposite moralities. It eventually creates a heroic Skeletor who helps the heroes. When the double and real Skeletor fight, the heroes can't tell them apart, until He-Man asks both of them to say, "He-Man, I am your friend." The double says it without hesitation, while the real Skeletor angrily refuses.
  • Matt's Monsters: One episode has the team face off against Dink's evil cousin, who looks exactly like him, so naturally this scenario eventually comes up. Matt is able to sort out who is the real Dink by throwing a popcorn kernel at the two, which Dink immediatly pops with his electricity while his cousin doesn't react to it.

    Real Life 
  • Boston landmark Faneuil Hall has an unusually shaped weathervane (a grasshopper), which was sometimes used as a Spot the Impostor test during the American Revolutionary War.
  • Alan Turing proposed that a computer program which could win a text-only game of Spot the Imposter should be considered intelligent. The "Turing Test", as it's called, is a popular challenge for A.I. programmers to try to overcome, though it isn't seriously considered a benchmark for true intelligence in a computer. The original paper is available online, for the curious.
  • During the Battle of the Bulge, German troops in US Army uniform infiltrated the lines with the intent of causing sabotage and disruption. Checkpoints grilled GIs on things every true-blooded American was expected to know such as the identity of Mickey Mouse's girlfriend, baseball scores, or the capital of Illinois. This last question resulted in the brief detention of General Bradley; although he gave the correct answer (Springfield) the GI who questioned him apparently believed the capital was Chicago. Although this behavior is often ridiculed in fictional depictions of the battle, it did succeed in identifying a number of infiltrators, many of whom didn't speak fluent English or know anything about American society. There's also a legend about a German spy who was caught because he could recite the entire "Star-Spangled Banner" when no true American knows anything past the first verse.
    • Other things that gave the infiltrators away were that the Germans would pack four men in a jeep and drive it with the black-out slits on the headlights. The well-equipped US troops drove one or two men per jeep, and being used to their side having air superiority didn't bother with the black-out covers.
  • Similar to the above, the parts of the French Resistance that helped Allied pilots back to England often quizzed the airmen they were helping. They often came across pilots who had knowledge of their unit, but none of their supposed home town, who were immediately detained as a possible mole. Once, they had a pilot who was the opposite — knew everything about his homeland, but nothing about his unit. Fortunately for him, one of the Resistance members was able to contact the RAF and established that he had been transferred there as a replacement from another unit, then immediately put on a bomber that was shot down over Europe.

    One Allied pilot who was shot down and hidden in a barn by some locals found himself woken in the middle of the night by someone jabbing him in the gut and screaming at him in German. He reflexively protested in his native English, which served to prove to the French partisans that he was not a German spy. He reflected later on that it was fortunate that he did not reflexively reply in German, which he had studied in school.
  • As The Other Wiki states, it helps if there is some handy phrase that your side can pronounce but which the enemy find difficult.
  • There have been accounts of World War II German soldiers spotting careless spies at rallies because they saluted wrong.
    • Likewise, other careless slips, such as cutting and eating a steak the wrong way.
    • One Axis Powers Hetalia skit told a similar story about a German Spy in France: He was found out when he ordered a meal with a whole cooked potato. Apparently, Germans mash a whole potato while Frenchmen dice it.
    • Or, in one case, a colorblind POW that wasn't aware that British and German uniforms were not the same color.
  • According to US Air Force tradition, the Challenge Coin became a tradition during World War I after an American pilot who had been shot down, captured by the Germans, then later escaped, having only a medallion with his unit's insignia engraved on it (his identification documents having been confiscated by the Germans). This at a time when it was common for infiltrators to don enemy uniforms to sneak into enemy camps and conduct recon and sabotage.

Alternative Title(s): Spot The Impostor