History Main / SpotTheImposter

** In ''[[Manga/JoJosBizarreAdventureStardustCrusaders Stardust Crusaders]]'', 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 how: 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 effect exists, but the captain had given himself away with that action.

* ''ComicBook/PowerPack'': in "X-Men and Power Pack #2" of the all-ages series, [[Characters/MarvelComicsMystique Mystique]] impersonates Jack Power in order to escape the heroes. At [[Characters/XMenTheOriginalTeam 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.

* ''ComicBook/PowerPack'': in "X-Men and Power Pack #2" of the all-ages series, Characters/{{Mystique}} impersonates Jack Power in order to escape the heroes. At [[Characters/XMenTheOriginalTeam 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.

* In the Alabasta arc in ''Manga/OnePiece'', [[{{shapeshifting}} 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.

* Done in ''Film/TheIsland'', with a twist: the impostor was the ''protagonist''.

* ''Sev Trek: Pus in Boots'' (an Australian CGI spoof of ''Series/StarTrekTheNextGeneration''). The crew find themselves confronted with two Captain [[PunnyName Pinchhards]], one of them a shapeshifting alien. Lt. Barf wants to [[KillUsBoth kill them both]], as the alien would [[ThisWasHisTrueForm 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.

'''Pinchhard:''' Oh please! I slept through the whole thing!\\

* ''WesternAnimation/ToyStory2''. 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 [[WesternAnimation/ToyStory1 the first movie]]. He clinches the identification by showing the toys the name "Andy" on the sole of his boot.

** ''Point Blanc'' ends with a genuinely disturbing sequence in which Alex and [[CloningBlues 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, [[AmbiguousCloneEnding even when one falls into an inferno]]. In the next book, everything's all fine and dandy with Alex being the survivor, but...

* ''LightNovel/HaruhiSuzumiya'': Koizumi notes that as he's basically a tool of Haruhi's subconscious, he can easily identify her in any situation. [[spoiler:Unfortunately, the reason this comes up is because Kuyoh is trying to kill someone who appears to be Haruhi--and Koizumi confirms that yes, it is her.]]

* ''Anime/{{Pokemon}}'':

** In ''Manga/StardustCrusaders'', 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 how: 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 effect exists, but the captain had given himself away with that action.
** At one point in ''Manga/DiamondIsUnbreakable'', 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 [[DumbMuscle he's not that smart and was just going to punch out the other guy too.]]

** A ''Comicbook/FantasticFour'' and ''ComicBook/SpiderMan'' story resolves the situation of the Chameleon impersonating Spider-Man in a distinctive manner. ComicBook/TheThing, holding one in each hand, throws both several meters into the air. The Chameleon reveals himself by screaming in terror and the ComicBook/HumanTorch 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.

** In ''ComicBook/SpiderManLifeStory'', an aged Peter and Miles Morales are on a mission and attacked by a Venom-symbiote infected Kraven. After defeating it, Peter notes "all my enemies are dead. Isn't that right...[[spoiler: ''Otto''?" Dr. Octopus demands to know how Peter figured out he had taken over Miles' body.]] Peter relates it was "the little things" such as [[spoiler: "Miles" being more serious and calling him "Parker"; calling Kraven by his first name as if he knew him; the symbiote stopping an attack as it sensed what happened and laughing "well played, old friend." The clincher was that not only was Miles using technology more than he used to but it was rather outdated, as if designed by a genius scientist stuck in the past.]]

* In ''ComicBook/Supergirl2005'' ''ComicBook/GirlPower'' storyline, [[EvilTwin Dark Supergirl]] switches her costume with the original ComicBook/{{Supergirl}}'s at super-speed, in an attempt to fool Batman and ComicBook/{{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 ComicBook/WonderWoman to use her Lasso of Truth.

* In the final issue of a short-lived mid-70s comic named after and starring ComicBook/TheJoker, 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 ''ComicBook/SecretInvasion'' (the main mini-series): In Issue #8, BackFromTheDead ComicBook/{{Mockingbird}} is confronted by her ex-husband, Comicbook/{{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.

* ''ComicBook/PowerPack'': in "X-Men and Power Pack #2" of the all-ages series, ComicBook/{{Mystique}} impersonates Jack Power in order to escape the heroes. At ComicBook/{{Beast|MarvelComics}}'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.

** While she can copy someone's appearance, Mystique can't replicate powers. Thus, all it takes is seeing, say, ComicBook/{{Cyclops}} not firing eye beams or ComicBook/KittyPryde not phasing to realize who this is.
** DependingOnTheWriter, ComicBook/{{Wolverine}} (or others with heightened senses) can sniff out Mystique but other times, they'll be caught off-guard. Likewise, sometimes son ComicBook/{{Nightcrawler}} and foster daughter ComicBook/{{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.

** The X-Men are fighting the Starjammers who they think are being mind-controlled and thus holding back. Corsair blasts ComicBook/{{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.

** ''ComicBook/WonderWoman1987'': Heading to rescue Steve Trevor from shapeshifting Durlans, ComicBook/WonderWoman and ComicBook/CaptainAtom 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.

** ''Stay Out of the Basement'' involves a plant clone. [[spoiler: 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 [[PlotAllergy his food allergy]] to prove that he's not the evil clone. [[spoiler: 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]].

* Played straight in ''Anime/FullmetalALchemist2003''. 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.

* Subverted in ''Manga/FullmetalAlchemist'' when [[spoiler:Mustang and Hawkeye]] are confronting [[spoiler: 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 [[YouJustToldMe she was lying]], but he'd already given himself away]].
** Played straight in [[Anime/FullmetalAlchemist 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.

* Literature/TheBible makes this OlderThanFeudalism. From 1 Kings 3:16-28, 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 [[JudgmentOfSolomon 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 gave up her claim rather than let the baby be killed was judged to be the true mother. Also likely the origin of the "kill both of us" gambit, though that is a variation.

* In one episode of ''Anime/FutariWaPrettyCure'', Nagisa is confronted by two Honokas (one of them being Poisony in disguise), and has to figure out which is the real one. She asks them a series of questions relating to her, and both answer all of them with no issue. The real Honoka eventually reveals herself when she mentions Nagisa's stinky socks, which only she would know about.

* In one episode of ''Anime/GhostInTheShellStandAloneComplex'', 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 [[ViewersAreGeniuses lets you figure it out for yourself]] instead of spelling it out for you.

* 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, who last won the World Series, 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.

* Satirised in [[https://gatogordito.wordpress.com/2012/03/14/112/ "Quick Solution"]] by Wordpress user Gato Gordito; a boy having to decide which of his mothers is a robot imposter solves the issue by playing the Xbox 360. His real mother [[PopculturalOsmosis mistakes it for Nintendo]], so he shoots the robot imposter, who identifies it as an Xbox 360.

* The plot of ''The Tightrope Men'' by Desmond Bagley involves a man who has been altered by plastic surgery to resemble a KidnappedScientist. 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 LongList of trick questions because she's tumbled to the fact that he's an imposter.

[[folder: Audio Drama]]

* Subverted in ''Webcomic/DeadOfSummer''. The deal with [[spoiler: Panther and his clone]] seems to be leading into this, as the two meet face to face...and the real [[spoiler: Panther]] takes the clone out in one blow.

* Satirised in [[https://gatogordito.wordpress.com/2012/03/14/112/ "Quick Solution"]] by Wordpress user Gato Gordito; a boy having to decide which of his mothers is a robot imposter solves the issue by playing the Xbox 360. His real mother [[PopculturalOsmosis mistakes it for Nintendo]], so he shoots the robot imposter, who identifies it as a Xbox 360.
* In the ''Webcomic/{{Narbonic}}'' storyline "Professor Madblood and the Doppelganger Gambit", Dave is transmogrified into Madblood to infiltrate his moonbase, and then hides amongst Madblood's robot duplicates when the real Madblood returns. Madblood decides to flush out the imposter by [[http://narbonic.com/comic/march-10-15-2003/ making the androids sing the "Madblood Battle Anthem"]], since the imposter wouldn't know that. However, the androids don't know it either, [[ComicallyMissingThePoint so Madblood teaches it to them]]. [[spoiler: This turns out to work anyway because Dave is so ''enthusiastic'' about singing it]]. Later in the same storyline, Madblood uses the transmogrifier to pose as Dave. While he's [[http://narbonic.com/comic/march-31-april-5-2003/ completely unconvincing]] when he contacts Helen, Mell is confused when she sees [[http://narbonic.com/comic/april-21-26-2003/ two Daves fighting over cigarettes]], and it doesn't help that Artie, having been sent to the Moon in a faulty teleporter, now ''also'' looks like Dave.

* As [[Website/{{Wikipedia}} The Other Wiki]] states, [[http://en.wikipedia.org/wiki/Shibboleth it helps if there is some handy phrase that your side can pronounce but which the enemy find difficult.]] One such example is Denmark’s prized porridge rødgrød. It was so hard to say that “rødgrød med fløde“ (literally ”rødgrød with cream”) has been used by the Danish to catch infiltrators in BOTH World Wars.

[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/diltondanni_waifu2x_art_noise1.png]]

[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/diltondanni_waifu2x_art_noise1.png

[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/dss.png]]
[[caption-width-right:350:Can you tell which one's which?]]

[[quoteright:251:[[Franchise/ArchieComics https://static.tvtropes.org/pmwiki/pub/images/Dilton_Impostor_4491.jpg]]]]
[[caption-width-right:251:Can you tell which one's which?]]

* As [[Wiki/{{Wikipedia}} The Other Wiki]] states, [[http://en.wikipedia.org/wiki/Shibboleth it helps if there is some handy phrase that your side can pronounce but which the enemy find difficult.]] One such example is Denmark’s prized porridge rødgrød. It was so hard to say that “rødgrød med fløde“ (literally ”rødgrød with cream”) has been used by the Danish to catch infiltrators in BOTH World Wars.

* 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.

** ''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 [[PlotAllergy 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.

* ''Machinima/RedVsBlue Revelations'':

* Played straight in ''Machinima/TheGmodIdiotBox''. Louis is trying to decide which Francis is real (one is a spy). He tells them to go up stairs. The one that gladly does gets shot. It then gets parodied the next moment, when Louis decides that they have to go up the stairs, [[spoiler:and the real Francis hates stairs, so he shoots Louis]].