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Spotting the Thread

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"A web of lies can unravel with the lightest touch of the truth!"
Othar Tryggvassen (Gentleman Adventurer!), Girl Genius

This is when an impersonator has an almost perfect disguise, only to ruin it with a seemingly inconspicuous mistake. Perhaps the impostor blurted out something out-of-character (or a personal catchphrase), forgot to include a Distinguishing Mark (often an Intimate Mark), or accidentally revealed that they're left-handed. This can more easily occur during a round of Bluff the Imposter, and can be a sub-trope of Spot the Impostor except that their target generally has no advance knowledge that there is an impostor in the first place.

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Related to Pull the Thread, as this is often what leads to it. Compare Saying Too Much, a more incriminating version. See also Conviction by Counterfactual Clue, when this gets even more unrealistic, and Conviction by Contradiction, which overlooks that there may be a perfectly reasonable explanation for the discrepancy. Often overlaps with Imposter Forgot One Detail. Compare For Want of a Nail.

When applied to a dream test, it's A Glitch in the Matrix or a Revealing Continuity Lapse. See also I Never Told You My Name and I Never Said It Was Poison, when the impostor gives themselves away by revealing they know something they shouldn't, or Confronting Your Impostor, which is what happens when somebody stumbles upon somebody else pretending to be them.


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Examples:

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  • Played for Laughs in a Bush's Baked Beans Ad, in one of talking dog Duke's attempts to get the secret family recipe from his owner by posing as Grandpa Bush's ghost:
    Duke dressed as ghost: How did you know it was me?
    Jay Bush: Grandpa didn't have a tail.

    Film — Animated 
  • Incredibles 2: Elastigirl twigs on to something being wrong with her infiltration of the Screenslaver's lair when she wonders why the Screenslaver, who obviously had access to a lot of resources, only used mundane deadbolt locks on his door. She then realizes that the Screenslaver she fought was a fake when she figures out that the heavy goggles he was wearing could serve as the screens for the Screenslaver to control him. She also notices that footage from her mask is being broadcast on Screenslaver's TV, when the mask is supposed to be closed circuit.
  • Leroy & Stitch: When Leroy disguises himself as Stitch after he has been kidnapped, Lilo was able to tell he was an imposter because he was not wearing the tiki necklace she gave the real Stitch prior to his departure from Earth.
  • Megamind:
    • In the climactic battle, Titan realizes that Metroman is actually Megamind in disguise due to the distinctive way he mispronounces Metro City.
    • Although it serves as Five-Second Foreshadowing, Roxanne realizes that Metroman's hideout can't be as abandoned as it seems because there's still a drink with unmelted ice on the side.
  • In The Road to El Dorado, the two con-men protagonists convince the natives of El Dorado that they are gods in human form. However, the high priest Tzekal-Kan realizes the truth when he sees that Miguel has a bleeding cut from playing ball (think full-contact Mayincatec basketball) against a team of natives.
    Tzekal-Kan: Do you know why the gods demand blood sacrifices? Because gods don't bleed.
  • Wreck-It Ralph: Ralph realizes that something suspicious is going on in Sugar Rush when he notices that there’s a picture of Vanellope on the side of the arcade machine, contrary to King Candy’s claim that she’s a glitch character that was never supposed to be in the game.
  • Rango has to use a Snowball Lie to bluff his way out of one of these, when he claims to have killed the Jenkins brothers with one bullet and is immediately asked "All seven of them?"
  • Batman: Assault on Arkham: Batman, suspecting that Harley Quinn deliberately let herself get captured, takes a look at Arkham security camera feeds. He recognizes guards who shouldn't be there that night and realizes that he's seeing recorded footage from the previous day.

    Film — Live-Action 
  • In the Taiwanese spy-action film 21 Red List, the Japanese double-agent, Kiki, lies to protagonist Chi-wu that she's been in the shower while waiting for him in his bedroom, when she's actually searching his room for the titular list. Chi-wu however sees through her lies because even though the bathroom's floor is wet, there isn't any steam on the mirrors.
  • In Attack of the Killer Tomatoes!, "Master of Disguise" Sam Smith blows his cover after infiltrating the tomato camp, by asking for ketchup to put on the arm he's about to eat.
  • A Beautiful Mind: a variation: this is how John Nash finally realizes his chronic hallucinations. One of his hallucinations is a young girl, but even though he's seen her for years, she's never grown any older.
  • In Big Eyes, when Margaret finds a shipping box of paintings by S. Cenic in the closet, which helps her realize that Walter had been lying about painting in Paris.
  • The point of the Voight-Kampff Test in Blade Runner is to spot the thread for Replicants. Replicants are biological androids completely identical to humans down to blood, sweat and bad breath, but they have no empathy. The test involves asking questions that would provoke an empathetic response in a human and note when the replicant fails to show any physical signs.
  • The Bodyguard From Beijing: John is able to tell apart assassins and common civilians during the mall shootout, because the assassins all have pens clipped to their pockets. A supposedly cowering civilian gets gunned down by John the moment he sees the pen on his front, dropping his pistol in the process.
  • In the documentary Catfish, Nev begins to realize Megan is not real because he finds out she took other people's songs and said they were hers.
  • The Da Vinci Code: zigzagged. Bank manager Andre Vernet is helping the protagonists flee the police by putting them in a truck and pretending to be the driver. A detective, though, notices a Rolex on his hand and wonders how a truck driver can afford it. Without skipping a beat, Vernet convincingly plays it off as a fake he bought from some shady dealer and even offers to sell it to the cop for cheap.
  • Delta Force 2: The Colombian Connection has a US Agent able to get close to the Big Bad, Ramon Cota, and become his second in command. However, he gives himself up when he sets up Cota's arrest during his flight on a private jet, because he was the only person Cota told about it.
  • In Die Hard 2: Die Harder, McClane notices two men sitting at a table who, despite being dressed in business casual attire, are wearing combat boots rather than appropriate shoes. Becoming suspicious he follows them, reports them, discovers they are Mooks of the Big Bad who are up to no good, and does everything in his power to foil them, which would have worked without a hitch if the cops in the airport weren't such belligerent, incompetent assholes.
  • In Die Hard with a Vengeance, McClane gets in an elevator with several terrorists disguised as cops and security. He notices they're using terminology incorrectly, referring to the elevator as a "lift" (a European/British term) and a weather report as raining "dogs and cats" (instead of "cats and dogs"). McClane is visibly suspicious, and spots that "Detective Otto" is wearing a police badge that belongs to a friend of his. He assesses whether anyone in the elevator is a real cop by asking what the lottery numbers were last night, since it's been established that all New York cops play the lottery. When no one knows, McClane realizes that they're all imposters.
  • In Double Indemnity Keyes is entirely satisfied that the late Mr. Dietrichson's death was not suspicious and entirely accidental...until he realizes that the man had broken his leg right after signing up for a generous accident coverage policy, yet he didn't file a claim for his leg. This is the first piece of evidence that Dietrichson didn't even know about the policy in question.
  • Dredd:
    • Judge Dredd trips up a corrupt Judge on Ma-Ma's payroll this way. When the Judge states that he was responding to a call for backup, Dredd points out that the Judge didn't ask about the rookie Anderson; Dredd was alone in hostile territory at the time, and a Judge really responding to such a call for Dredd and Anderson would have have asked where the missing rookie was.
    • The same thing happens with the rookie herself. The corrupt woman Judge of the group sent by Ma-Ma claims she will kill the rookie, because as a Judge, Anderson is likely to trust her and hesitate. Anderson, being psychic, sees through the deception almost immediately and kills the corrupt judge after a brief exchange.
  • Enola Holmes: At the end of the film, Enola receives a coded letter from her mother just as she had been hoping for all movie. However, she quickly realises that it was actually written by her older brother Sherlock because firstly, it was signed 'Mother' when her mother would use a codename and secondly, as a radical feminist in Victorian London Enola's mother would never arrange to meet her at the Royal Society, an institute that routinely snubbed female applicants.
  • In A Few Good Men, an Armor-Piercing Question shatters Col. Jessup's confidence in his testimony. Jessup had kept his cool, arrogantly stating that his orders have always been followed and that he did not order the Code Red. Kaffee seizes on the Logic Bomb: if Jessup gave an order that Santiago wasn't to be touched, and his orders are always followed as he so claims, then why would Santiago be in danger, and why would it be necessary to transfer him off the base? Jessup clearly looking uncomfortable and fumbling over his words is a clue that the trial has taken a turn.
  • Get Smart: Max spots the traitor because, after visiting the Big Bad's destroyed lair and reporting that there was no longer any active uranium there, the traitor sets off the Geiger counter concealed in Max's watch. On mentioning this he then spots that the traitor's stab wound is freshly bleeding, as if nerves of being detected were prompting a higher blood flow.
  • In Ghost Ship, Epps catches on that the villain has killed and impersonated her last remaining crewmate when he doesn't ask her what happened to the second-to-last one, who's been killed in the interim. He drops the act and admits he already knows because he killed the other one too.
  • The climax of The Godfather Part II is a famous example. When Fredo first arrives in Havana, he tells Michael that he's never met Hyman Roth or his lieutenant Johnny Ola. Later, when Michael and Fredo are watching a lurid live show at a nightclub with Johnny and a few other family associates, Fredo gets excited and accidentally mentions that he took Johnny to see the show a few days previously. Turns out that Fredo and Johnny have met before, but Fredo lied and claimed that they hadn't. From this tiny slip-up, Michael is able to figure out that Fredo has betrayed the family, and is working with Hyman Roth to bring him down.
  • In Godzilla (2014), after breaking back into old Janjira, after it was quarantined due to a reactor meltdown, Joe Brody realizes the place isn't radioactive when he spots three dogs chasing each other, when they should be dead from radiation. A quick check of his Geiger counter confirms his suspicions.
  • In the 1974 film Godzilla vs. Mechagodzilla, the human protagonists begin to suspect that the disguised Mechagodzilla is a fake when it attacks Anguirus...something the REAL Godzilla wouldn't do since he and Anguirus are allies. Their suspicions are confirmed when the original Godzilla shows up to do battle against Mechagodzilla for the first time. Anguirus also immediately notices that the disguised Mechagodzilla is a fake because it doesn't sound or act like the Godzilla he knows.
  • In The Gourmet Detective, title character Henry Ross realises that an alleged ‘suicide message’ he received on his answering machine was faked when he realises that it records a one o’clock and two o’clock chime from a distinctive clock in the same message fifteen seconds apart, thus confirming that it was actually created from a series of other conversations spliced together.
  • The Great Escape: This is how Bartlett and MacDonald are captured. A Gestapo agent asks to see their identification and asks them questions in French, as their cover identities are French businessmen. When he is finished, he says "good luck" to them in English, and MacDonald blunders by replying in English. A case of Truth in Television; this is pretty much exactly how Roger Bushell (the basis for the Bartlett character) was caught in the real escape (see "Real Life").
  • In Hangmen Also Die!, Inspector Gruber figures out that Dr. Svoboda and Mascha weren't actually having an affair when he sees lipstick smeared on his own cheek in the mirror, recalling that the lipstick mark on Dr. Svoboda's cheek was immaculate and thus deducing that it must have been placed there intentionally to throw him off their scent by making it seem like what they were up to was having an affair.
  • Harry Potter:
    • In Harry Potter and the Chamber of Secrets, Harry and Ron's plan to disguise themselves as Crabbe and Goyle is nearly undone at the start when Malfoy notices "Goyle" wearing glasses. When Harry gives the excuse he was reading, Malfoy's response is "READING?!......I didn't know you could read."note 
    • Harry Potter and the Goblet of Fire: Barty Crouch Jr. used a Polyjuice potion to disguise himself as Mad-eye Moody. However, Barty Crouch Sr. spotted "Moody" doing Junior's signature tongue-flick, which gave him away. Note this was only done in the film version.
  • This is a plot point in The Hateful Eight, as soon as Major Marquis Warren arrives at Minny's Haberdashery he immediately notices that things are wrong. For example: a single jelly bean is lying on the ground far away from its storage jar, visitors are wearing hats inside (which the rules of the haberdashery don't allow), Minny is said to be on vacation (a flimsy story), Minny's famous stew is still fresh despite the fact that she's been gone for a while according to Bob, guests are sitting on Sweet Dave's chair (which would never be allowed), and Bob (a Mexican) has been hired to watch over the haberdashery while Minny is "gone" (Minny hates Mexicans so she would never do this.) His suspicions are proven to be correct.
  • In Hot Pursuit, cop Cooper and drug lord wife Daniella barely escape when masked killers shoot up a mansion. Cooper calls for help and is met at a diner by cops Dixon and Hauser who said they were responding to her call. Cooper reflects on how she only put out the call 20 minutes earlier and to arrive here from the station so fast, Dixon and Hauser would have had to have been doing 180 miles an hour. She then sees their car's fuel gauge indicating they have only traveled about 30 miles which is where the mansion was. The clincher comes when Cooper sees Hauser has the same arm tattoo as one of the masked gunmen.
  • In Inception there's an example of literally spotting the thread, when Saito notices that the carpet in a room he's in is made of the wrong fibre, tipping him off that he's still in a dream.
  • Inglourious Basterds, Deiter Hellstrom notes that the Inglourious Basterds pretending to be German officers are behaving strangely. He also says that Lieutenant Hicox's German accent sounds strange. Hicox covers for himself by saying that he's from a small Swiss mountain village with a unique regional accent. This seems to quell Hellstrom's suspicions, but then he asks for three drinks with the wrong hand gesture, using "index-middle-ring" and not "thumb-index-middle", as Germans usually do it. This finally convinces Hellstrom that he's an impostor.
  • The Italian Job (2003) has this: Steve realizes Stella is John's daughter because of a phrase she uses, that he's never heard from anyone one else but John.
    Steve: Still don't trust me?
    Stella: I trust everyone. I just don't trust the devil inside them.
  • James Bond:
    • In From Russia with Love, Red Grant is impersonating Captain Nash, Bond's MI6 contact in Yugoslavia. Bond is initially suspicious as "Nash" calls him "Old Man" rather than "Old Chap" like a Briton would, so he inspects his briefcase and finds the standard-issue MI6 equipment, allaying his fears. However, during dinner, Nash orders red wine with his seafood dish rather than white wine, something that no cultured Briton would do, he "accidentally" spills Tatiana Romanova's glass and slips some pills in while refilling it and toasts with "cheero" instead of "cheerio". Bond starts to see that Nash isn't who he seems, however, he doesn't put two and two together till after Grant gets the drop on him.
    • In You Only Live Twice, Blofeld sees through Bond's astronaut disguise when he attempts to enter the capsule while carrying his air conditioner unit in his hand, something a real astronaut would never do.
    • In Tomorrow Never Dies, Elliot Carver's tech assistant Gupta immediately uncovers Bond's secret identity. The tech calls it "Gupta's Law of Creative Anomaly", and explains that anyone's personnel record is bound to have errors and flaws. Bond's fake banker profile is too perfect, meaning he's obviously a government agent.
    • In Quantum of Solace, M wants to know if the CIA is interested in Dominic Greene, so she calls their head office and asks about it. She's routed to the CIA section chief for South America, who denies having any interest in him. M immediately concludes that he's lying because they automatically routed her to the highest-ranking officer in the region of the world Greene is in, which they wouldn't have done if they weren't already tracking him.
  • In The Last Witch Hunter, Kaulder has a penchant for spotting those.
    • He realizes that something's sketchy about 36th Dolan's demise when he notes that retirony is normally not Truth in Television.
    • The illusion that 36th Dolan's house is neatly cleaned up is shattered when he notices a Plague Fly - a dead-ringer for Dark Magic - dead on the floor of a house which was locked up for the entire day. When he tests the house for Black Magic because of it, Glamour Failure ensues.
    • His clue to Ellic being part of a gang rather than a singular assassin is the fact that Ellic is too low-level a warlock to perform shapeshifting Kaulder's seen him wear.
  • In Legally Blonde, Elle Woods, during the climactic trial, notices that Chutney Windham's testimony included the claim that she had gotten a perm and then taken a shower soon after, just before the incident in which she claimed that Elle's client shot her father. Knowing that you're not supposed to get your hair wet for twenty-four hours after a perm, Elle uses this fact in order to tear Chutney's case against her client apart, eventually finding out that Chutney had shot her father herself when she had sought to kill the client instead, since she'd been angry about her father taking up with someone who was the same age as his daughter.
  • Marvel Cinematic Universe:
    • Captain America: The First Avenger:
      • Steve Rogers wakes up in a 1940s-era room. A woman wearing a period-specific military uniform enters to greet him. Rogers catches on that something is amiss when he remembers being at a baseball game that was seemingly broadcast live over a radio in the same room.
      • In a meta example, viewers familiar with 1940s period fashion can tell the scene is in the present and not a dream because the agent is wearing a bra that's noticeable through her shirt (the cups of 40's era bras would have fit closer to the chest). Also, while her hair is curly (as was the style in the 1940s), the curls are much too small and haphazard to be true Victory Curls. Steve seems to notice something is off about her appearance from the second he sees her.
    • Captain America: The Winter Soldier:
      • Steve notices an ammo bunker at what's left of the decommissioned Camp Lehigh that's way too close to the barracks for either safety or Army regulations. It turns out to be the secret base holding Zola's uploaded brain.
      • Earlier in the film Steve realizes the friends and colleagues piling into the elevator with him on apparently innocent business are there to attack or restrain him because he spots the tell-tale signs of nervousness and weapon-readiness they are trying to conceal. Being Steve Rogers, he gives away the element of surprise by asking if anyone wants to opt out of the coming fight.
    • Captain Marvel:
      • After lecturing Carol that everyone calls him Fury, and absolutely no one calls him anything else, Fury is on high alert when another agent calls him "Nicholas". Carol is also able to track another Skrull onto a train when they assume the form of an old woman...whom Carol had run into by accident getting off of the train just before getting on the train herself. This small detail also comes into play for the audience in ''Spider-Man: Far From Home, as "Maria Hill" refers to Fury as "Nicholas" in the beginning, hinting that "Fury" is really Talos the Skrull.
      • A double-whammy when Yon-Rogg confronts Carol near the end of the movie: "Carol" answers his questions perfectly until he presses "her" for more detail and "she" slips up. This both clues him in to "Carol" being a Skrull and to "Vers" having turned on him.
  • In Mission: Impossible – Ghost Protocol, murderous thief Sabine is canny enough to know that IMF is after the intelligence she stole (killing IMF Agent Hanaway to do so), and realizes that Ethan and Brandt are IMF agents when she sees Brandt's hi-tech contact lens, which Hanaway had been wearing when she killed him at the start of the film.
  • Not Okay: Harper realizes Danni's lies about going to Paris as Danni said it was clear then, but actually the city had rain at the time. Then there was how Danni claimed to have toured Notre Dame Cathedral, which would have been hard given it was shut down after the massive 2019 fire. She then dug deeper into it and uncovered that this was all made up. She gives Danni the choice between coming clean herself or Harper blowing the lid. Danni chooses the former.
  • In Our Man Flint, the protagonist reveals two fake guards that have had plastic surgery to look exactly like the regular ones. The give-away is that they wear uniform ribbons made from an existing - but unofficial - medal. Flint spots this at first glance.
  • In Paycheck, Jennings suspects that the Rachel he meets in the cafe is an impostor when he sees a colored contact lens shift out of position while they kiss.
  • The ending of Primal Fear has Martin Vail realize something is off when his client, Aaron, said "I hope her neck is okay." The injury he refers to happened during an attack made by his split-personality, during which Aaron allegedly has no memory - and yet he apparently knew about where "Roy" had attacked the prosecutor.
  • In Rags, Lloyd manages to discover that Charlie is Rags by noticing a conspicuous signature on Rags' shoes, which matches the one on Charlie's.
  • Zigzagged in Scream (1996): Billy Loomis, who has been suspected of being the killer for the entire movie, and even taken into custody at one point (although he was later cleared) is asked by his girlfriend Sidney who he called with his "One Phone Call" when he was arrested. He tells her that he called his father, but Sidney points out that the station called his father. Not thirty seconds later, he is killed, exonerating him from suspicion. However, it turns out that he actually was the killer (or one of them anyway) and had faked his death, and the thread Sidney had spotted earlier was probably correct.
  • This happens at near the end of Scream 4. After it seems like the latest Ghostface Sidney's cousin, Jill, got away with the perfect crime in murdering Sidney, and replacing her as the Final Girl, she makes a fatal mistake. She tells Dewey about her arm injury pointing out how it was the same injury Gale Weathers had. When Dewey mentioned this to his on-again, off-again life mate, she points out that Jill could only have gotten the same injury if she was the Ghostface who attacked her at the annual Stab party. Before they can expose Jill, Sidney fights and kills her after Jill found out she was still alive and tried to finish the job.
  • In Sherlock Holmes: A Game of Shadows, Holmes and Watson find which of the ambassadors at the peace summit has been replaced by an impostor when Watson deliberately knocks a tray of glasses over. The fake is the only one who doesn't turn and look, being too enveloped in his role to produce a spontaneous reaction.
  • in Stalag 17, the Germans have planted a spy, Price, in a POW camp posing as an American flier from Cleveland. Sefton (William Holden) suspects the ruse, and in the climactic scene confronts Price:
    Sefton: When was Pearl Harbor, Price, or don't you know that?
    Price: December 7th, '41.
    Sefton: What time?
    Price: 6:00. I was having dinner.
    Sefton: 6:00 in Berlin. [To the other barrack members:] They were having lunch in Cleveland.
  • In Star Trek IV: The Voyage Home, Kirk and party are within seconds of successfully bluffing their way out of the hospital with the wounded Chekov in tow when this exchange occurs.
    Guard: How's the patient, Doctor?
    Kirk: He's going to make it.
    Guard: He? They went in with a she.
    Kirk: (to himself) One little mistake...[they run]
  • In Star Trek V: The Final Frontier, Kirk finds something off in "God's" demands for his followers:
    "God": This...starship...could it carry my...wisdom beyond the Barrier?
    Sybok: It could! Yes!
    "God": Then I shall make use of this starship.
    Sybok: It will be your chariot!
    Kirk: Excuse me...
    "God": It will carry my power through every corner of Creation...
    Kirk: Excuse me, I'd just like to ask a question...What does God need with a starship?
  • The dramatic thrust of Sucker Punch is almost entirely dependent on whether or not the audience can do this. There's a really big clue, though, just before The Reveal that a twist is coming because a character's wearing a dress she shouldn't have.
  • The ending of the 1974 version of The Taking of Pelham One Two Three has the last remaining hijacker accidentally giving away his identity with his recognizable sneeze.
  • Titanic (1997): Jack talks down a suicidal Rose, while removing his jacket and shoes incase he has to jump in to save her. Unwilling to admit this, they claim she simply slipped and he pulled her back up (which did happen). Lovejoy immediately spots the flaw, if she slipped so suddenly, how could Jack have had time to remove his jacket and shoes? It is unclear however if he works out the truth.
  • In Transformers: Age of Extinction, when Cade is trying to deny any knowledge of Optimus Prime to the CIA, he refers to Optimus as "he", alerting Attinger that Cade must have spoken to Optimus if he was using gender-pronouns. Flimsy evidence, but they ain't exactly worried about due process.
  • In The Truman Show, the world Truman spent his entire life in starts collapsing as he begins noticing multiple threads pulling apart.
    • In particular, there's a point where he observes that a lady on a red bike, a man with flowers, and a vintage Volkswagen beetle with a dented fender, go around the block, over and over again, and always in the exact same order at the exact same time.
    • During the "Nuclear Meltdown" encountered during his escape attempt, his reaction to a police officer uttering "You're welcome, Truman." without ever asking his name or being shown any ID.
    • The writers handwave the falling spotlight as a falling piece of a random satellite, but that's a pretty blatant lie for us.
    • One day when Truman is driving into work, his radio starts picking up interference and he notices that it's narrating everything he's doing (which the radio show host handwaves as being interference from a police scanner).
    • Meryl's attempt to cheer Truman up with cocoa backfires when he notices how she's giving him an obvious, stilted sales pitch for that cocoa, leading to a heated argument which ends with him holding a kitchen gadget to her neck, at which point she yells "do something" at a hidden camera.
    • While looking at his wedding album, he notices a photo showing Meryl doing a Lying Finger Cross.
    • In a deleted scene, Truman gives his sandwich to a man in a wheelchair, and two days later he notices the same man jogging like he's in perfect health. He's even wearing the same shoes.
    • To the audience, the town Truman is living in is obviously fake looking but Truman grew up in that setting so to him all the oddities look perfectly normal. However, the cost of maintaining an entire fake town would be enormous and it's clear that the producers have been Cutting Corners. Sets are reused, same extras are used for multiple roles and continuity is not adhered to. Truman has been basically brainwashed to accept everything that is happening as normal and not to question things that are out of place, but the anomalies are allowed to get so out of control that even Truman realizes that things are massively wrong in his life.
  • In Truth, bloggers examine memos used in support of a 60 Minutes broadcast and find out that the memos, allegedly typed in the 1970s, could be reproduced perfectly with the default settings of Microsoft Word, and early 1970s machines that could have produced the memos would not have been available to the alleged author.
  • At the end of The Usual Suspects, as Agent Kujan believes he figured out that the testimony he just heard from Verbal Kint was meant to protect Dean Keaton's identity of Keyser Söze, his gaze lingers on the overcrowded billboard of his colleague and makes a connection between its brand ("Quartet" from Skokie, IL) and a seemingly irrelevant anecdote Verbal told earlier about having been "in a barbershop quartet in Skokie, Illinois". From there, Kujan realizes that every detail from Verbal's story has been made up based on names pulled from the billboard for the purpose of buying time until he was bailed out and that Verbal Kint was actually Keyser Söze all along.
  • In Warcraft (2016), Khadgar realizes that something doesn't add up in Medivh's behaviour when the latter burns down his research on the Portal.
  • In Wild Wild West, Jim West immediately recognizes that Artemis Gordon is not the real President Grant (he was basically practicing his decoy costume). When Gordon asks what the tipoff was, West points out his class ring — it identifies him as a Harvard graduate, and President Grant attended West Point. Of course, there's a very good reason why the make-up was so good - Grant and Gordon are played by the same actor.
  • Winterskin: One morning, Billy comments that Agnes slept surprisingly soundly for someone who's deathly afraid of skinless monsters breaking into her door in the middle of the night. That's because she was lying to make him stay with her. The only actual skinless monster he ever faces is his father, after Agnes skins him.
  • In Wishmaster, Alex eventually catches on that the Djinn disguised himself as one of her friends. The Djinn manages to explain a Saying Too Much slip-up, but his antagonistic behavior and constant offers to do something for her (thereby invoking a wish) give him away.
  • In X2: X-Men United, Wolverine figures out Mystique isn't Jean because she has the scars where he stabbed her in the previous movie. Later in the same movie, Stryker takes one look at Mystique from across a large room and knows she's not Wolverine simply saying "I know my own work".
  • xXx:
    • Xander Cage spotting the fake diner hold-up and critiquing everyone in on it due to all the dangling threads he spotted within a minute:
      Xander: You know, you almost had me going there for a while. I was a bit groggy before, then I started noticing things. Like, you got a stockbroker over here, all dressed up, reading the Financial Times on a Sunday morning when the market's closed. Unlikely, but okay, I can go with that. I can even go with the stick-up man packing a cop-issue Beretta. But you want to know where you blew it? With her. [points to the waitress] My aunt was in the restaurant business all her life. There's no way in hell a career waitress comes to work in high heels. She'd have blisters the size of pancakes before lunch. And if she ain't real, then this whole thing ain't real. That's how I knew this bozo over here wouldn't get a shot off even if we waited till St. Patrick's Day. Because there's nothing but blanks in these guns. Oh, and no offense, but their performances were terrible.
    • Subverted in the next scene when Xander assumes they are still playing with him after dumping him in Columbian drug cartel territory. He figures it out just before Danny Trejo goes to work on him with a machete.
    • In the sequel, Xander is at a market square when a man comes up, strikes up a conversation with Xander, and leaves a bag behind. Xander looks in to find a ticking bomb seconds before a SWAT team runs in to arrest him. Rolling his eyes, Xander takes down a cop and spins around, firing his machine gun, showing it's full of blanks. He relates how he knew it was a test: A teen is listening to expensive headphones rather than the cheaper knock-offs; a woman is running to catch a bus that won't leave for two hours; a "cop" is paying for a drink with foreign currency; and the old man struck up a conversation somehow knowing ahead of time that Xander spoke English.
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    Literature 
  • The Adventures of Huckleberry Finn: Huck goes in disguise as a girl at one point; the woman he's talking to gets suspicious when he attempts to thread a needle by putting the needle onto the thread, whereas any girl would know that it is far easier to do it the other way around, and ultimately is found out when he catches a ball of yarn tossed to him via closing his legs such that it lands on his lap. A girl would instead open her legs to catch it on her skirt. In short, Huck didn't do his research.
  • Agatha H. and the Siege of Mechanicsburg: When Klaus claims that Gil was wasped before he even met Agatha, Gil claims she never gave him any orders. Boris immediately realizes that she did—she politely asked them all to leave (which might not have counted) and screamed a Big "NO!" (which definitely counted). The fact that Gil easily ignored both orders means he can't have been wasped.
  • In Animorphs, Jake winds up infested by a Yeerk after falling into a Yeerk pool. When "Jake" spots Ax (an Andalite, whose species are at war with the Yeerks), his face momentarily contorts into a look of hate, alerting everyone to the problem; the Yeerk blows it even worse when Ax touches him, at which point he yells "GET YOUR HANDS OFF ME, ANDALITE FILTH!". The other Animorphs also point out that if Jake was really the one "in the driver's seat", he would have gone along with their plan to starve the Yeerk just to make absolutely sure and settle everyone’s minds. But since the Yeerk was fighting them every step of the way, the other Animorphs tied him up, knowing with 100% surety that he was a Controller.
  • In the BattleTech novel The Sword and the Dagger, it's revealed that Hanse Davion, the First Prince of the Federated Suns, has been replaced with an impostor because the impostor can't pilot Hanse's personal Battlemaster, since the neurohelmet a mechwarrior wears to give their mech balance has to be carefully calibrated to the mechwarrior's brainwave pattern.
  • In The Book of the New Sun, Severian spots a literal thread: a ribbon sticking out from the side of the head of the mysterious soldier he battles at the Sanguinary Fields, which should tip him off that it's really Agilus in disguise. Severian spots the clue, but cannot remember where he has seen such a thing before until two chapters later, after he has almost been killed in the totally unnecessary duel. It's a tip-off to the reader. As a famously Unreliable Narrator, because he's not as clever as he appears, Severian often mentions threads, but fails to pull them. And if Severian can't unravel this clue, how can he be expected to unravel the fact that he's being manipulated by time-traveling aliens?
  • In Bulldog Drummond, Drummond is able to recognise the Comte de Guy as Peterson in disguise, though he looks completely different, because he has the same unconscious mannerism when he's feeling impatient.
  • Clive Cussler is fond of this in many of his books from Spot the Impostor to figuring out clues behind some event.
    • In Iceberg, Dirk Pitt instantly knows something is up with Kristi as she is supposed to have spent years living in the jungles of South America but her tan is far too shallow.
    • In The Mediterranean Caper, Pitt finds it odd that Bruno Von Till, who boasts of his past as a World War I combat pilot, would have a model of a submarine in his study. This leads to his investigation that Von Till is actually wanted Nazi war criminal Admiral Eric Heibert.
    • The same novel has Pitt managing to spot the clues to tell him cop Darius is The Mole for Von Till.
  • Night Probe has former MI-6 agent Shaw (who may or not truly be James Bond) brought to his old headquarters to be recruited into a mission. After agreeing, Shaw asks why they bothered using a building that quite clearly has been deserted for years from the amount of dust around to the lack of a regular staff. The head agent admits it was both to set Shaw at ease and test his observation skills.
    • After a younger agent mocks his age at an airport, Shaw puts him in his place by pointing out how a "businessman" has been following them for the last ten minutes to a flight attendant at a terminal where her airline doesn't have any flights.
  • In The Oregon Files novel Skeleton Coast, Sloane Macintryre shocks Juan by being the first person to see through the Oregon's facade of a run-down tramp ship. She's spotted several of the crewmembers wearing clothing or watches far too expensive for a crew barely scraping by. Also, having grown up around boats all her life, she knows there's no way the Oregon can be moving so fast without highly advanced turbines developed after it was built. The fact the ship was moving when the bridge telegram was at "all stop" and it took several minutes for the "smokestacks" to billow out smoke added to it. The clincher is her pulling back a painting on the wall to reveal a hidden camera as she'd seen Juan glancing to it a few times during their talk.
  • In Zero Dawn, Pitt has a computer search uncover that over 80 people died on April 18th, 1906, all at almost the same time at different places but each obit almost exactly the same with just a few words changed. They all actually died in an experiment gone wrong (which inadvertently caused the San Francisco Earthquake) and the government hushed it up. Lampshaded by the government agent dryly stating that in 1906, no one was really considering the possibility some fancy machine would be able to see through the pattern.
  • The Isaac Bell series focuses on a detective who's a master of spotting the tiny details (such as figuring out a man faked being knocked out in a fight as his eyes are still very alert rather than showing the effects of a blow).
  • In Codex Alera, Magnus figures out that First Spear Valiar Marcus is actually the traitorous Cursor Fidelias by spotting a number of such threads, such as Marcus being able to reliably spot him when he's trying to be stealthy, and seemingly having disappeared off the face of Carna after serving his military term (because Fidelias abandoned that cover identity after serving his time, later reusing it to spy on the First Aleran).
  • Basically the reason the fake meteorite is exposed in Dan Brown's novel Deception Point; all the evidence supported the idea that the meteor in the iceberg was real, but once they discovered a few microscopic fish under the meteorite, introducing the idea that it had been planted in that iceberg on purpose, Rachel, Michael and Corky are able to take another look at the evidence and admit that there are other explanations for the evidence beyond it coming from outer space.
  • In Do Androids Dream of Electric Sheep?, Deckard is initially led to believe that he's registered a "false positive" on Rachel Rosen's Voight-Kampff test (ie. he's identified a real human with stunted empathy as an android, something that would have invalidated the entire testing process and forced Earth's police agencies to come up with a whole new test from scratch). The Rosens, apparently looking to protect their own reputation, try to buy his silence on the matter by bribing him with their (very rare) pet owl, but when Rachel continuously refers to the owl as "it" instead of "she", Deckard realizes he's been had: Rachel is an android, and the Rosens were trying to set him up to blackmail him into dropping his investigation.
  • In Double Star by Robert A. Heinlein, an actor is hired to double for a prominent politician who has been kidnapped, and spends weeks studying the politician's files on everyone around him to make the masquerade work. He notices that the file on the emperor is nearly empty, and assumes that they don't have much contact...until he meets the emperor, and gets found out, because why would you need files to remember how you deal with your longtime friend? He's caught when he dutifully plays with the emperor's toy trains instead of teasing him about them.
    "It was not until later that I realized that the file had not been defective, in view of the theory on which it was based, i.e., it was intended to let a famous man remember details about the less famous. But that was precisely what the Emperor was not—less famous, I mean. Of course Bonforte needed no notes..."
  • The Dresden Files: In Battle Ground Ethniu shows Harry a memory pulled from her mortal soldiers showing them entering the Carpenter home and massacring everyone inside, including Maggie. Harry quickly figures out it's a setup since the memory has no sign of Mouse. This thread was deliberately left by Molly when she designed the illusions the soldiers "killed" so Harry would see through Ethniu's manipulation.
  • In Dale Brown's Edge of Battle, Jason tries to disguise himself as a Mexican to infiltrate a meeting by the villains, which works until one mook notices that he has a gringo's blue eyes.
  • Discussed in The Emperor's Soul by Wan ShaiLu, a Master Forger whose work requires her to be a polymath with an exacting eye for detail. When she learns that the Emperor is brain-dead and a government faction is trying to hide that fact by keeping him "in seclusion", her first instruction is that someone regularly fill the Imperial chamber pot, because servants would notice if he stopped using the toilet.
  • In the Georgette Heyer novel False Colours, Kit is caught in a Twin Switch when he opens a snuffbox the wrong way.
  • Garrett, P.I.: In Faded Steel Heat, Garrett is impersonated by a shape shifter, who visits Morley Dotes' restaurant to find out how much Garrett's friends know. The phony is exposed almost immediately, as Morley's waiters offer "Garrett" a platter of roasted green peppers, and the fake tucks into it at once. The offered platter had been a prank, as steak-loving Garrett has spent several books denigrating Dotes's vegetarian menu, and green peppers in particular. Note that they did know shape shifters were around, so it wasn't that huge leap from 'Garrett acting unusual' to suspecting it was a 'shifter. Flushing them out was actually one of the reasons for feeding him that meal.
  • In Ghost, when looking for a nuclear bomb in the press parking lot at Notre Dame, where the Pope was scheduled to speak, Mike identifies the enemy agent when he claims to be from Alabama, but is eating his meal in the Continental style (not switching the fork to the right hand to cut with a knife in the left) instead of the American one.
  • Ghost Roads: Bethany gets Rose a wrap for her dress, so she'll have a "coat" that won't stand out at the dance. She says she was able to match the color from the yearbook picture. Thing is, though, Rose died before she made it to prom, so there aren't any pictures of her in her dress. This is an early clue that Bethany is working with Bobby Cross.
  • Harry Potter
    • Harry and Ron make some errors when they turn into Crabbe and Goyle in Chamber of Secrets, although Malfoy apparently doesn't think anything of it other than that his friends are acting a bit weird today. For example, they forget that they're supposed to laugh at Malfoy's jokes and Ron corrects Malfoy when he gets Percy's name wrong.
    • In Goblet of Fire, Dumbledore realized that something was up with "Moody" when he removed Harry from Dumbledore's sight—the safest place he could be—in the midst of all the chaos surrounding Cedric's death.
    • Harry Potter and the Deathly Hallows: At Fleur and Bill's wedding, Harry uses the Polyjuice Potion to disguise himself. It doesn't fool Luna Lovegood, who recognizes him from his expression.
    • A villainous example: In Hallows, the Death Eaters realize which one of the several Harrys are the real one when he uses his "signature" spell, Expelliarmus.
    • Also in Deathly Hallows, Harry, Ron and Hermione go to visit Xenophilius Lovegood in order to find out more about the Hallows. To their surprise, Lovegood is rather reluctant to talk to them, even though he had been using his magazine to support Harry. All through their meeting, Lovegood acts very strange, and it isn't until Harry goes to Luna's bedroom and notices a thick layer of dust on the furniture that he realizes Lovegood had been lying to them about Luna being down by the river in order to get them to stay put long enough for him to call the Death Eaters so they could be captured.
  • Honor Harrington:
    • In Echoes of Honor, a Haven admiral notices that the prison planet Hades has been taken over because the warden has been playing a game of chess with him (move by move, by courier ship), and the warden's move doesn't arrive when it should.
      • It's worth noting that the rest of his command staff thinks he's insane for sending a whole battle fleet to investigate on the basis of a missing chess move. He is, however, right.
    • Used deliberately when a Solarian supposedly assisting Haven's State Sec digitally alters the uniforms and bridge of the State Sec crew to look Manticoran when they communicate with an Andermani warship. The Andermani commander realizes immediately that someone is trying to con him because the Solarian secretly inserted a CGI "extra" in the background of the bridge, one that looks exactly like Honor Harrington. Not only did the commander know her personally, having met in the past, at the time she was thought dead after being executed by the People's Republic of Haven.
  • The Hunger Games: The official, "live-action" shots of District 13 are revealed to be Stock Footage by a mockingjay which flies past the screen at the exact same spot despite claims that it is filmed repeatedly every year.
  • House of Robots: Robots Go Wild!: Sammy notices that Eddie Ignalls keeps getting the name of his brother, Freddie, wrong. Whenever he points it out, Eddie covers it up by saying it's his middle name or a nickname. In truth, there is no Freddy Ignalls. It's just a ruse to get SS-10K into the school and close to E so he can sabotage him.
  • In Into the Drowning Deep, sirens can perfectly mimic any sound they hear, but they can only repeat it exactly and have no sense of the context of the sounds most of the time. As such, they can be found out when they do things like mimic the sound of a boat motor a mile under the surface or repeat the same whale song regardless of circumstance.
  • Maximum Ride's clone might have been a more successful replacement if she had known that the blind guy was the Team Chef, but given that the flock's youngest member is a freakin' mind reader the chances are slim.
  • In the Philip K. Dick short story Precious Artefact, the reconstruction engineer first suspects on returning from Mars that the Earth streets he's seeing aren't real when his coin falls through a dispenser. This is later confirmed for him when his houseplant, in Earth's supposedly more humid environment, dies of dehydration.
  • Rivers of London: In The Hanging Tree, the sight of an expensive mechanical watch on Martin Chorley's wrist — one without microchips that can be destroyed by magic — tips Peter off that Chorley is almost certainly the Faceless Man.
  • In Santiago: A Myth of the Far Future, Cain is caught in a vision of being on his home planet by Altair of Altair. When he's asked by Altair, in the guise of a girl he had a crush on, to drop the "stick" (his gun) and help her across a brook, he shoots her and tells the corpse that his home planet doesn't have any brooks.
  • In Shaman Blues, Witkacy spots that something doesn't quite match in Tadeusz Dzwon's story by the man's brief terror at the very mention of his sister, putting the detective on fast track to figuring out the murderer.
  • Star Wars Legends: Galaxy of Fear has a spot of this in Clones. Our heroes have been separated and Tash is on the run from a number of her own clones, commanded by a clone of Darth Vader. When she's menaced by a clone of Hoole, she's saved by Zak, who then wants her to punch in a code to summon their ship...but then she remembers that both of them are supposed to know the code, so why hasn't he done it? Yep, he's a clone too, and goes on the attack as soon as she figures it out.
  • Agatha Christie's Tommy and Tuppence book N or M?: Tuppence does this almost literally. Her fake identity, "Mrs. Blenkensop," is not good at knitting, but Tuppence is. At one point, she gets distracted and Mrs. Blenkensop suddenly starts knitting perfectly. She tells the others who witness this that she was pretending to be a poor knitter so one of the other residents at the hotel would have an excuse to help her.
  • Tortall Universe:
    • Aly does her best to avoid mistakes of this kind in the Trickster's Duet and pretend to be a simple country maid while posing as a slave in the Copper Isles instead of the highly educated daughter of Sir Alanna, King's Champion of Tortall. This is made difficult when Sarai and Dove don't want to hear about anything but Alanna, and Dove notes every slip.
    • Beka Cooper:
      • An illegal slave sale in Terrier is found out by the spotting of several such threads in the announcement they sent out. The threads were these: They used pure red wax for seals (the legitimate version includes ebony shavings), used a cotton ribbon (legitimate announcements use silk), misnamed the king, and wrote the letter "s" normally (scribes at the Ministry of Slave Sales put an extra curl on the letter "s").
      • Bloodhound: Beka notices a man trying to exchange counterfeit silver coins for copper ones because it's too early in the evening for most Lower City residents to have silver (gambling starts later at night, and gambling is the only real way for most to get silver). When she investigates further, she notices that the profile on the coins is pointed in the wrong direction. The man is quickly caught.
  • In The Unexplored Summon://Blood-Sign, Kyousuke first suspects that Aoi is actually the White Queen when she doesn't forget about him when he's out of her sight (in the setting, normal people can't remember anything about summoners outside their field of vision). This wasn't certain evidence on its own, since Aoi is an Artificial Human to which this might not apply. The key evidence is "Aoi" using a specific technique for squirting water with one's hands, which Kyousuke originally taught to the White Queen. However, it's implied that these slip-ups may have actually been deliberate, given that the end of that novel reveals that the White Queen wanted Kyousuke to defeat her.
  • Vorkosigan Saga: Invoked at one point in Cetaganda, when the Barrayarian Embassy's "protocol officer" Colonel Vorreedi has a talk with one of the young officers sent to officially represent his homeworld at a State Funeral. With a few leading questions on both sides he swiftly sees the truth behind Miles, Lord Vorkosigan's cover as the Prime Minister's half-crippled son being given a sinecure to keep him out of everyone's hair...aside from the detail that he was not at the moment on a top secret covert ops mission at the behest of ImpSec director Simon Illyan himself.
    • In The Warrior's Apprentice, one character video-calls his friend and ally. The call keeps having static in between responses. Miles notices that one object on the desk moves between responses, and correctly deduces that the call stitched together from multiple recordings, and the static is to cover up the cuts. The guy they're "talking" to was captured long ago.
  • Warhammer 40,000: Eisenhorn:
    Eisenhorn: You could talk like Nayl and use Glossia thanks to Jekud, but Jekud didn't know what Nayl knew. We fought Sadia on Lethe Eleven, not Eechan.
  • In The Witchlands, Cam realizes that Vivia might not be the person behind the assassination attempt on Merik when she learns that the Empress of Marstok, whose well-being doesn't interest Vivia in the slightest, has been attacked in the same way.
  • In a Russian fantasy novel Wolfhound the titular hero exposes a disguised assassin when he notices that although the man wears a distinct native costume, the patterns on his shirt and boots do not match and indicate him as a member of two different clans at the same time.
  • In Keith Laumer's Worlds of the Imperium, the protagonist is recruited as a spy because his counterpart in an alternate universe was a ruthless dictator, and the plan was to replace his double to allow for a successful revolution. The plan works and he's successful in convincing everyone he's the dictator...up until the moment, flush with how successful the masquerade has been, he stands to greet one of the dictator's confidants and is immediately exposed. No one outside the dictator's immediate circle knew he's lost the use of his legs.
  • Mistborn: The Kandra can easily shapeshift into anyone whose body they've eaten, except for their hair, which they need to transplant strand by strand. In Wax and Wayne, Wayne muses that he should keep an eye out for someone without any hair on their..,arms.
    • In a later book, when the crew is searching for a treasure in a temple, the last chamber contains an empty pedestal next to some broken glass. Wax realizes that this was only meant to look like a robbery when he measures the broken glass, and finds that if the glass case was reassembled, it would be too big to fit on the pedestal.
  • In Outpost, Striker and Hop approach Councilman Golm during his regular lunchtime park outing. After realizing the Councilman is likely the bait, Striker looks around, initially seeing nothing out of the ordinary. Then he notices four things: there are no kids in the park, even though it's a popular place for school field trips; the two old ladies walking past them were carrying bags that looks far too heavy, and they themselves looked more muscular than their wrinkles would suggest; a young couple was sitting on the next bench over, even though lovers generally preferred to find isolated spots; and there were three blue-collar workers in a central city park, wearing coveralls, in the middle of a workday. Striker and Hop barely manage to get away, and only because of this and because Fiddler was acting as a Friendly Sniper.
  • The Alice Network: Rene realizes Eve isn't from the French region she claims based on her accent. She allays suspicions by lying that she traveled from there for work, and didn't want to say anything since that's very near the German border, thus many French people would suspect that she's a collaborator.
  • Discworld: Multiple cases in the Watch books alone.
    • When dealing with Inigo Skinner in The Fifth Elephant, Vimes concludes that his walk is so visibly harmless that it's suspicious and lobs an orange at him; it bounces off Skinner as he acts shocked that Vimes threw the orange at him. This makes Vimes even more suspicious of him, though, as most people would either catch or dodge (confirmed by throwing an orange at another member of the Watch, who reacts appropriately), but Skinner saw in an instant that it wasn't a threat. Then he sends Skinner's description back and gets confirmation that he's an Assassin.
    • Also subverted in The Fifth Elephant; the replica Scone of Stone is made of plaster and anyone who takes a close enough look should spot it. Albrecht, in accordance with tradition, signs off on the fake Scone as genuine anyway. It's already been replaced multiple times, and Albrecht's family knows it; one more isn't going to be a problem.
    • Anyone with a reasonable ability to read people spots that Vimes is used to more serious command than being "Sergeant-at-Arms John Keel" in Night Watch Discworld.
    • In Snuff, Vimes spots that someone is masquerading as a sailor because an actual sailor would have sea-legs and be more functional on a rough sea.

    Myths & Religion 
  • In Classical Mythology, this is what leads to the nymph Echo's tragic fate. She's a known Motor Mouth who can't resist getting the "last word" whenever she talks to someone else. One day, she encounters Zeus having one of his many trysts in the woods—and then runs into Hera, who's angrily looking for her cheating husband. Echo covers for Zeus by luring Hera into a lengthy conversation, giving him time to send his lover away. Hera leaves, and Zeus thanks Echo for her kindness by giving her a valuable ring. When Hera comes back to ask Echo one final time if she's seen Zeus, she claims innocence...but Hera notices the ring she's now wearing and realizes what happened. Furious, the goddess curses Echo to only be able to repeat the last word that other people say for all eternity (the echoes we hear in canyons and cliffs are the lamentations of Echo herself).

    Podcasts 
  • In episode 11 of Sequinox, it seems like the girls have gotten back to their world. Then Yuki notices that instead of the clothing they had that morning, their outfits are colour-coded. Then it turns out that this isn't their world, it's a Power Rangers-themed world.
    • Again in episode 14, right down to them thinking they're back. Then they notice Caiden wearing glasses. It's a superhero world, and Caiden is Clark Kenting.

    Tabletop Games 
  • The Demoreans of Timemaster are prone to being caught this way. Their obsession with "Perfection" means that when they capture someone and take his place, they don't include any scars or "deformations" (such as a missing fingertip) that the original may have had.

    Theatre 
  • In The Pajama Party Murders, Lola's disguise as Myrtle is revealed when someone points out that, after being called Uncle Cosmo's non-swearing, non-drinking missionary, she swore and took a swig of beer. From there, Pettibone runs down a list of clues that she was an impostor.
  • Mary from The Children's Hour has convinced her grandmother that her two teachers are having a lesbian affair. Her grandmother is an influential person and within days all the students have been taken away by their parents. When Karen and Martha confront Mary's grandmother about her Malicious Slander they ask Mary to explain. Mary keeps to her lie however she says she saw the two doing things when she looked through the keyhole to Martha's door. The problem is, as Martha angrily points out, her door doesn't have a keyhole. Mary then switches her lie to having heard noises from Karen's room, however Karen's room is too far for anyone to have heard anything. When she can't figure out a new excuse Mary says she heard the rumor from a classmate, who heard it when the door was open. Mary blackmails Rosalie to get her to agree with the lie. Karen and Martha spot the thread, however everyone else believes the kids including Karen's fiance.
  • In the beginning of Act 2 of Les Misérables, Javert disguises himself as a disgruntled ex-soldier who helps out the revolutionaries by acting as a spy and attempting to feed them false information. He's only found out when Gavroche reveals him as a cop. It's a wonder they didn't realize this earlier, as Eponine's panicked warning in The Robbery indicates that he's a quite well-known police officer, and he had interacted with three of the revolutionaries (Marius, Gavroche, and Eponine herself) before going undercover.
  • National Theatre's 2014 production of Treasure Island:
    • After Jim overhears the pirates plotting mutiny and reports it to Captain Smollett, Smollett nearly manages to maneuver the would-be mutineers into going ashore where they can be threatened with marooning, pretending that he's unaware of their treachery and offering them the first chance to set foot on dry land after the long voyage. Jim accidentally blows the gaff by making a comment about Long John Silver having been on the island before; Silver recalls that he's been careful never to mention that fact except to his fellow mutineers, realizing that this means Jim heard their conversation.
    • Near the end, Trelawney tries to bluff the pirates by pretending to be the ghostly voice of the late Captain Flint. Armed with details about them supplied by Ben Gunn, he nearly pulls it off until Silver gets suspicious because "Flint" also knows the name of a mutineer who threw in with the pirates on this voyage and was never part of Flint's crew.

    Visual Novels 
  • Quite often in the Ace Attorney series. The defense attorney you're playing as needs to spot a contradiction in a witness testimony, present a theory, and back it up with evidence. Inevitably, this results in some Courtroom Antics to help catch the real criminal.
    • During case 4 of the first Ace Attorney game, Phoenix Wright completely bluffs about how someone who had been shot could have carried a bullet from the scene of a crime...and, following it to its logical conclusion, helps prove it.
    • Ace Attorney Investigations 2 has a prisoner impersonating a security guard, only to get uncovered when his pet polar bear goes to him.
  • Danganronpa: Trigger Happy Havoc: During the second scene of the game, the main character will note that Junko Enoshima looks different from her cover shots on magazines. This is then played off as the result of touch-ups and editing. Some of her dialogue during Free Time events also seems incongruous with her Ultimate Fashionista title. Chapter 6 reveals that the girl everyone met at the start was not Junko, but rather her fraternal twin sister Mukuro Ikusaba, whose appearance is very similar, but with a few minor differences.

    Webcomics 
  • In Cuanta Vida, Jeremy's green eyes and relaxed attitude tip off Jordi that he's dealing with Miguel, the RED spy.
  • Shapeshifting fae Nutmeg from Dan and Mab's Furry Adventures pretends to be her husband, but Mab notices it because she didn't get the mannerism and hoof patterns right. Earlier, Jyrras uses a Magitek patch to pretend to be a cubi, but the disguise is pretty transparent to any real cubi (who are mind readers).
  • In this strip of Girl Genius, despite being in pain from having just swallowed a slaver wasp, Baron Klaus Wulfenbach is able to tell the person he's talking to isn't Agatha Heterodyne from her speech pattern, facial expression and body stance...and he finally recognizes she's (possessed by) Lucrezia from hearing her gloat.
  • In El Goonish Shive, Tom's apology to Susan for missing her on a text messaging service tips Susan off that his intentions are not what they seem to be on the surface. He never asked whether or not she'd been online with that messenger service that night before apologizing for "missing" her online...and the messenger service has an "invisible" mode.
  • The Order of the Stick:
    • At one point Elan is replaced by his Evil Twin Nale, despite pretty much every thing he does being a possible invocation of this trope, all his teammates just chalk it up to Elan being, well, Elan. Until that is Nale changes out of the clothes he stole from Elan and takes a shower, at which point Belkar notices that "Elan" smells like Nale.
    • Elan himself realizes that the team have been trapped in a Lotus-Eater Machine when Nale doesn't do anything to stop their parents remarrying. This realisation forces him to acknowledge that the remarriage doesn't make sense either, it's just what he'd want to happen.
    • When Nale is later trapped in the same Lotus-Eater Machine, he snaps out of the illusion after realising that he had been monologuing to a captive Elan and Haley for over an hour and that they hadn't escaped his clutches in that time.
  • Plane-spotters and birdwatchers do this in this xkcd strip, much to the frustration of a government cabal who now need to find a new disguise for their surveillance drones that doesn't have an obsessive spotting community. Turns out, there's a lot of people who like staring at the sky.

    Web Original 
  • At times, This Very Wiki. That "Super Secret Spoiler" wasn't so Super Secret when some extra white space where there shouldn't be popped up.
    • Of course, due to the YMMV finagle, Super Secret Spoiler has been replaced with the normal spoiler.
    • Averted deliberately by some clever tropers by using completely unnecessary spoiler space or adding innocuous information under spoilers in strategic places, and making spoilers longer . . . yes, longer than necessary so their length doesn't give anything away, such as the hidden text being the exact length of a character's name.
  • Parodied in SF Debris's reviews of Star Trek: Voyager, in which it turns out that all the hallucinations and fantasies share one common flaw: Chakotay is too lifelike.
  • Help Not Wanted: Ogrell Syn'Gorrsh speaks in Third-Person Person all the time, but in chapter 6, he tells the four goblin contractors, "I'm not a trustworthy person." They realize immediately that he's been lying about who he says he is, and it's revealed that he's a Serial Killer who pretends to act stupid so his victims will lower their guard around him.
  • Loves Lost And Found: Maria is having dinner with a strigoi disguised as Hardestadt Delac. While in disguise, the strigoi calls Maria a woman, despite the fact that Maria is non-binary. They notice, and shortly afterwards, Maria kills the impostor.
  • In the Search and Rescue Woods Creepypasta series, the protagonist hears a crying child, and goes to investigate. He then notices something wrong: the "crying" is the same sound over and over again, like a song on repeat. He wisely nopes out of there.
  • In the When Posting Goes Wrong episode about the HIVLiving scandal from tumblr, a blogger named Ursula does this twice, which blows the whole thing open.
    • First, the lie that led to them confronting the mod of the HIVLiving blog, "Israa", who claimed to be an HIV+ sex trafficiking survivor living in India. Ursula suspected Israa wasn't being honest about her background or HIV status, and did some digging—which found a post she put up asking for donations, ostensibly for medical reasons. The problem? The app she asked people to use to send her money only worked in America.
    • This led to them confronting "Israa", who, after some prodding, admitted she was a college student named Alix living in the United States. However, she insisted Israa was real and that they were friends—and that she really was HIV+. Ursula, obviously, wasn't buying it, and continued to grill them for several hours, until finally catching Alix in a lie that they absolutely could not wiggle out of. Alix claimed to share a tumblr login with her roommate, which was already dubious at best, and then claimed her roommate didn't know she had HIV. Except, as Ursula points out, Alix frequently mentions her HIV status on her blog, including in her bio. If she and her roommate shared a login, there's no way she wouldn't have seen it.
      Alix: oh shit

    Western Animation 
  • In the Adventures of Sonic the Hedgehog episode "Tails' New Home", Sonic and Tails meet an elderly fox couple who are apparently Tails' long-lost parents. Sonic allows Tails to stay with the couple, and while reminiscing on their first meeting, remembers that Tails is Only Known By His Nickname, and on top of that, it's a nickname that Sonic gave him. If the couple really were Tails' parents, they would have called him "Miles". Sure enough, the 'parents' are actually some of Robotnik's robots in disguise.
  • Big City Greens: In "Gloria's Café", Gloria has the customers pose as ghosts to trick Officer Keys into thinking the secret café is haunted so he doesn't arrest her; however, Keys immediately realizes the "ghosts" were fake because none of them said boo.
  • Beast Wars: Megatron makes a clone of Dinobot that can't transform. Had Dinobot not taken care of the problem, this trope would've resulted.
  • In Code Lyoko episode "Franz Hopper", a Polymorphic Clone impersonates Franz Hopper to lure the heroes into a trap. Jeremie realizes he must be an impostor after the fake Franz mentions the destruction of his video diary (which occurred in a previous episode) — something that the real Franz Hopper couldn't have known about, but that XANA certainly did.
    • "XANA's Kiss" features an inversion where Odd figures out that the Yumi yelling at him is the real her because she calls him a peabrain, something XANA and therefore his clones would never do.
    • In "Distant Memory", after being in a simulation bubble, Aelita notices when her father forgets the name Skidbladnir from a book her father read to her as a child, and then adds later that if he knew anything about her, he would materialize her Missing Mom into it, since she'd give anything to see her again. This helps her deduce that "her father" is really XANA. On the opposite side of the coin, Yumi and Jeremie realize that Aelita is in said simulation bubble because of a chat message from her father, having known the fact that he wouldn't risk it with her, since XANA is actively trying to dump her into the Digital Sea to draw him out.
  • In the Codename: Kids Next Door episode "U.T.O.P.I.A.", Numbuh One crash lands on an island that's a complete kid paradise, which causes him to be suspicious from the start. He finds his team swimming in the island's swimming pool and they all convince him to drop his suspicions and just have fun. Numbuh One is about to, until he remembers, as established in earlier episodes, Numbuh Four can't swim. At that point, it's revealed that he's been trapped in a Lotus-Eater Machine.
  • DuckTales (2017):
    • In "Let's Get Dangerous!", Darkwing Duck reluctantly agrees to investigate the disappearance of Gosalyn Waddlemeyer's grandfather, who was build the R.A.M. Rod device for Taurus Bulba. Bulba claims that Waddlemeyer was dissipated into another dimension when he turned on the device, convinced there was a flaw that Bulba himself assured was non-existent. However, when Gosalyn steals the key to the R.A.M. Rod in an attempt to bring her grandfather back, Taurus claims the device isn't stable enough to search the dimensions for him. Darkwing quickly realizes something is amiss, and points out Bulba said that he told Waddlemeyer the device was perfectly fine, which Bulba hesitantly claims is the case. Darkwing and Gosyaln then decide to use the R.A.M. to find Waddlemeyer...and it's at this point that Bulba shows his true colors...
  • DC Animated Universe:
    • Justice League:
      • In the introductory episode of the Secret Society, Clayface attempts to lure Batman into a trap by impersonating The Flash and calling for "help" against a confederate super-villain. Batman arrives on scene to find that "Flash" appears to have things well in hand:
        "Flash": Looks like I didn't need your help after all, yo. But you can help me tie him up—
        Batman: (throws a batarang at Flash) Catch.
        (batarang hits and electrifies Flash, reverting him to Clayface)
        Batman: The real Flash would have been too fast for that.
        Clayface: ...What gave me away?
        Batman: You overplayed your part, "yo".
      • From the same show, Lex Luthor needs barely a glance at the Justice Lords (currently masquerading as the Justice League) to say, "It's not them." Of course, this might have something to do with all of them wearing completely different costumes. The fact that Superman had just lobotomized someone was also a big clue.
      • In Season 1's "In Blackest Night", Green Lantern is accused of blowing up a planet and killing its entire population. Superman and Martian Manhunter go to check it out and quickly realize that something is off: If the planet really was destroyed, then why has its moon maintained its orbit?
      • In "Legends", after the heroes find their first main clue that something is off about Seaboard City, they start noticing smaller imperfections. The local heroes always work with the same two cops, and the exact same ice cream truck is constantly roaming the city without ever stopping.
    • Batman Beyond: In "Shriek", Bruce Wayne realizes that "his" voice in his head is actually somebody else, since this voice calls him "Bruce", while Bruce refers to himself by a different name in his head. When Terry points out that Bruce isn't Batman anymore, Bruce just says "tell that to my subconscious".
    • Superman: The Animated Series: In "Knight Time", similar to the Billy and Mandy example below, Robin figures out that something is wrong with Bruce Wayne when he smiles on a recorded message.
    • Batman: The Animated Series: The Ninja Kyodai Ken realizes Bruce Wayne is Batman after fighting him in both identities; as Batman tells Alfred, to a trained martial artist, a fighting style is "like a fingerprint".
  • Ed, Edd n Eddy: In "A Twist of Ed", the Ed’s plan to get the Kankers to leave them alone once and for all by using Reverse Psychology, pretending to have fallen in love with them and harass them with unwanted affection the same way they have done to them. Ed and Double D both put on a very convincing performance and have the Kankers trembling in fear at their presence, but Eddy continues to be too scared of the Kankers to even try to flirt with them. When Double D forces Eddy to take a turn to seal the deal, the Kankers notice a nervous sweat drop roll down his face. This immediately tips them off that the Eds are only faking their attraction to them, which not only restores their own crushes on the Eds, but has them come up with a plan to trap them and take revenge on them by pretending to still be scared of them.
  • Foster's Home for Imaginary Friends: In the episode "Bloo's Brothers", Mac takes Bloo to Show-And-Tell, where he's such a hit that all the other kids at school decide then and there to imagine up their own Bloo knock-offs. Unfortunately, despite all their creative spins on the concept (the Bloo clones tend to look nothing like Bloo, and most are downright bizarre), they're all Jerkasses at heart just like the original and end up getting dropped off at Foster's, where Bloo wastes no time organizing them into an army to take over the world a 100-part choir. However, when Mac shows up with two tickets to the Ice Charades, the other Bloos scramble to impersonate the real one in the hopes of going to the show. In the end, Bloo is pitted against a nigh-perfect clone as Mac grills them both to try and determine which is the real one: the fake gives himself away by launching into a Glurge-filled friendship speech.
  • Gargoyles:
    • In one episode, Goliath is plagued by hallucinations, this being the work of the vengeful spirits of Hakon and the Captain, which culminates in Goliath being confronted with an illusion of his slaughtered clan members who blame him for their deaths. Goliath is able to see through the facade when Hakon and the Captain make the mistake of introducing an illusion of Goliath's former love Demona, who unbeknownst to them had escaped being massacred, cluing Goliath in that everything he's seen wasn't real.
    • After seemingly being freed from Avalon's power, Goliath, Elisa, Angela, and Bronx find themselves fourty years in a Bad Future where Manhattan is a Dystopia ruled by Xanatos. Throughout the episode, every attempt to save the city is foiled, allies die in droves, and it all ends with Golith on the verge of death. The only way to undo the damage is using the Phoenix Gate to travel back in time and Set Right What Once Went Wrong. Too weak to act further, Goliath takes the Gate out of his pouch and tells Elisa to take it. The thread is when Elisa insists that Goliath physically hand her the Phoenix Gate rather than just picking it off the ground. This makes Goliath realize the deception and exposes "Elisa" as Puck trying to trick Goliath into giving him the Phoenix Gate since by law he can't simply steal it.
  • Gravity Falls:
    • "Into the Bunker:" When Dipper asks for a sign to decide which Wendy is the impostor, the shapeshifter gives him a suggestive wink, which Dipper knows the real Wendy would not do as of yet, and the real Wendy gives a legitimate sign, so Dipper correctly strikes the impostor.
    • "Weirdmageddon Part 2: Escape to Reality:" In Mabeland, a frustrated Dipper talks to Wendy, who says that if Dipper were older, she might have wanted to date him. At first, Dipper gets really happy at the thought, until Wendy yet again gives him a wink, a Call-Back to "Into the Bunker", revealing that this Wendy is just a part of the fantasy world.
  • The Grim Adventures of Billy & Mandy: Nergal Jr. tries to impersonate Mandy, but Billy can tell it's off because she was smiling. Weird use of this trope, as Nergal Jr. keeps his distinct glasses even when disguised as others. Billy does notice the glasses, too, but it's the smile he brings up first.
  • Agent Jay may be the rookie in Men in Black, but his keen eye for finding anomalies in the many disguises aliens use while on Earth helps him hone in on potential threats more than once:
    • In "The Undercover Syndrome", Jay's pretending to be an alien dignitary's bodyguard for a treaty signing as an assassin is rumored to be gunning for him. On the side, he strikes up a conversation with MIB's translator Vonda who's also there; she mentions a restaurant on Mason Street in Harlem that they could check out afterwards. Later when the signing's about to take place, the disguised Jay sees her approaching and, drawing from his previous stint as an NYPD cop, suddenly realizes there is no Mason Street in Harlem. Turns out the real Vonda was kidnapped by the assassin who took her place and disguised itself as her. Jay acts quickly to save the dignitary from getting killed permanently.
    • In "The Neuralyzer Syndrome", Jay and Elle are driving around trying to find a disguised alien ship. A quick look at the skies over New York, and he singles out a blimp. Elle asks why a blimp over Yankee Stadium was odd — Jay notes there's no game that night.
    • In "The Out To Pasture Syndrome", after Zed had retired from MIB and had gotten neuralyzed per standard procedure Jay gets jumped by Alpha out in the field, who scans his memories (specifically those of Zed's retirement party) to find out where Zed had retired to so that he could go exact revenge. After Alpha leaves Jay gets picked up by Elle who reveals that Zed wasn't actually neuralyzed, he just heard Alpha had escaped Antarctica and took the opportunity to set up a sting operation with a fake retirement to lure Alpha in so that MIB could capture and keep a much closer eye on him. Everyone in MIB was in on the Massive Multiplayer Scam except Jay, who was the bait for Alpha to get the faked info from. Jay asks whether the neuralyzer they used on Zed was fake — Elle confirms it and asks if Jay knew. Jay didn't, but he did see that Zed's eyes didn't glaze over like those who are actually neuralyzed usually do. Elle then realizes that if Jay noticed that, so would Alpha. Indeed, Alpha counter-baits the waiting MIB agents into firing on a hologram before taking them out — Jay and Elle have to rush over to help Zed and Kay before they get killed by Alpha.
  • The Owl House episode "Labyrinth Runners" has an Emperor's Coven scout attempt to fool Gus and Hunter by using illusion magic to disguise themselves as Willow. Interestingly enough, it's Hunter who sees through the disguise precisely because he's known her for far less time (they were acting like the Shrinking Violet she was at the beginning of the series and he only met her after she Grew a Spine; Gus would be used to this behavior and find it less out of the ordinary).
  • In an episode of A Pup Named Scooby-Doo, after capturing the ghost of Pervis Parker (an Elvis Presley expy), and revealing it to be the owner of the Pervis Parker museum, Velma states she first became suspicious of him after he made a long complaint to the kids about business being terrible, but when Daphne bought tickets to the museum, he was easily able break her large bill.
  • One episode of Regular Show, "Temp Check", features this. Doug, a shapeshifting mole attempting to take over Rigby's identity, is for the most part successful in convincing Mordecai and his coworkers that he's the real Rigby, but Mordecai sees through the facade for two reasons: the real Rigby whining about being "replaced", and the fact that Doug hugged Mordecai just before that (an act established earlier on in the episode that Rigby himself would never do).
  • Rick and Morty: In "Total Rickall" the Smith home is invaded by shapeshifting alien parasites which can create or alter peoples' memories, making it seem like they were always part of their lives. Rick and the others are unable to figure out who's real and who's a parasite, until a "Eureka!" Moment where Morty realizes that the parasites can only create pleasant memories, meaning they can tell who's a real family member because they'll have bad memories of them. Turns out it's not a perfect method when Beth shoots Mr. Poopybutthole because she can't remember any bad memories with him, only to find out he was Real After All.
  • In the Rugrats episode "The Trial", the babies set up a trial to find out who broke Tommy's clown lamp with Angelica in the role of prosecutor. The babies realize at the end Angelica was the one who broke the lamp when her alibi of taking a nap at the time fell apart because she somehow knew everything the babies were doing. Because of her usual demeanor, Angelica gloats because she knows the babies can't say anything to the adults, but ends up outing herself anyways because she forgot Didi and Betty were in the next room and could hear everything.
  • Sonic Boom:
    • In the episode "Where Have All The Sonics Gone?", after Eggman and Morpho send Sonic to an alternate dimension, Morpho disguises himself as Sonic to keep up the charade for a little while and attempts to charm and invite Amy to a trip to the canyon. It only takes her a split second to realize what's going on (after giggling like a schoolgirl at the idea of going out with Sonic).
    • In the episode "Vector Detector", Vector the Crocodile is brought in to try to figure out who could have stolen Amy's hammer. When they find the culprit, comedian Wolf Sidekick, Amy is overly thrilled and mentions that her hammer is a one-of-a-kind weapon. This makes Vector realize that a comedian wouldn't want to take a mallet like hers when any old one would do. Thanks to some help from Sonic, Vector finds the real culprit — his manager, who had set the whole thing up for ratings.
  • In The Spectacular Spider-Man, Captain George Stacy is able to identify that someone is impersonating Spider-Man — twice — by observing the differences in build and height compared to the real thing. J. Jonah Jameson stumbles into the realization during the first instance when the real Spider-Man (who's currently wearing a different costume) immediately begins to push his buttons.
  • Spider-Man: The Animated Series:
    • Chameleon duplicates Nick Fury's appearance from his newspaper obituary, but the paper accidentally flipped the photo, putting his eyepatch on the wrong side. Spider-Man notices the difference immediately.
    • Later in the same episode, Chameleon poses as Peter Parker to get into position to kill his target. Spider-Man easily spots him (since Spidey, of course, is Peter Parker) and takes him out. As Chameleon is being taken away, he demands to know what was wrong with his disguise, at which point Spider-Man just makes something up.
  • Star Wars: The Bad Batch: In the pilot, the titular team learns of Order 66 upon its immediate issuance, acting confused as to what's going on. Hunter and Crosshair pursue the fleeing Padawan Caleb Dume (the future Kanan Jarrus from Rebels) and try to help him, but the latter tries to execute the order and kill the boy. Caleb escapes, but Hunter claims he shot the kid with a stun blaster as he was trying to jump over a cliff and fell to his death. Crosshair immediately gets suspicious when he sees Hunter looking towards the other side of the cliff, rather than down.
  • Star Wars: The Clone Wars: In "The Hidden Enemy", Rex and Cody begin investigating a possible traitor in their ranks. Learning that transmissions to the Separatists came from the barrack's of Sergeant Slick's platoon, they question the troops. One of them was cleaning his blaster, two were in the mess hall, and a fourth was in the medical bay. But the fifth, Chopper, lies about being in the mess hall at the same tame as the other two. He finally confesses he was making himself a trophy of battle droid fingers—something of which is against regulations—and his comrades think he's the turncoat. Slick tries to calm him down, leading Chopper to ask of his own whereabouts. Slick tells him they can work things out when the Jedi come back, but only Rex and Cody know that Anakin and Obi-Wan have left. This clues them in that Slick is the real traitor.
  • Star Wars Rebels: In "Through Imperial Eyes", Grand Admiral Thrawn is searching for the identity of The Mole in the Imperial ranks. After it seems that Lieutenant Lyste has been revealed as the traitor, having helped a rebel prisoner escape, a stormtrooper brings Thrawn the helmet the prisoner was wearing — which has a stylized lothcat painted on it, which Thrawn recognizes as being in the style of Sabine Wren. This leads him to deduce that Agent Kallus is actually the traitor, because the helmet most likely belongs to Ezra Bridger, who Kallus would have recognized, and the fact that he didn't report Ezra's presence...well.
  • Steven Universe: In "The Trial", the Defense Zircon spots several inconsistencies with the story of Rose shattering Pink Diamond. At this point, Rose Quartz was an infamous, wanted criminal, and the only one of her gem type that was active at the time. So how did she get past all of Pink Diamond's entourage without somebody recognizing her and at least sounding the alarm? On top of that, the explanation that Rose's sword shattered Pink Diamond makes no sense, because it was made so it couldn't shatter Gems, much less one of the most powerful Gems in the entire universe. The Defense Zircon concludes that Pink Diamond was killed by someone close to her, someone who could get past Pink's entourage with no interference, someone who'd have the authority to have the entire situation covered up, someone...like another Diamond. Of course, right after this, the Defense Zircon realizes what she just said and tries a Verbal Backspace, but the judge for the trial poofs her immediately.
    • Another instance, related to the same event: In "Your Mother and Mine", Garnet tells Steven the Crystal Gems' side of the story in a silhouetted flashback. Flashback!Rose Quartz wields her sword in her right hand, while the real Rose Quartz wielded her sword in her left hand, keeping her right hand for her shield (which Flashback!Rose didn't have).
    • In "A Single Pale Rose", the reason for the inconsistencies is revealed: Rose Quartz and Pink Diamond were one and the same. Her "shattering" was faked, with Pearl shapeshifted into "Rose".
  • Supa Strikas: In "Amal 3's a Crowd", as Supa Strikas play the Sultans FC in Dubai, they face a huge obstacle: The Amal 3, soccer-playing triplet brothers who can communicate telepathically...supposedly. Left-winger Cool Joe discovers the flaw; on the yacht after the brothers perform their world-famous "Three Blind Mice" routine during a party, two of the brothers bash heads with each other, temporarily breaking the ruse in front of Cool Joe and defender North Shaw. Initially assuming the threat was a 'three-headed snake', it turns out the threat is merely 'three snakes with one head'.

    Cool Joe: I was looking for clues in the FC Hydra match, our training sessions, and when they did their "Three Blind Mice" routine, but I was looking in all of the wrong places.
    Shakes: What do you mean, bro?
    Cool Joe: Back on the yacht, two of them bashed heads. If they can communicate with each other in their minds, why would they bump into each other like fools?
    North Shaw: So true, dude. Their brains were like, touching, and there was STILL no telepathy.
    Cool Joe: There is NO telepathy, man! Just well practiced routines. And there's only one man who calls all of the moves.
  • In Young Justice, Aqualad and Garth steal the uniforms of two of Black Manta's henchmen and try Dressing as the Enemy to get close. Black Manta sees through it pretty much immediately when he notices that Aqualad tucked his water-bearers into his belt.

    Real Life 
  • There is a story of a British spy in occupied France during WWII who was exposed after ordering "cafe noir" (black coffee). A local would have known that, with milk being scarce, the "noir" was redundant as that was all there was on offer.
    • Relatedly, hapless German and Russian spies in and after WWII ran into trouble when, if they made it to England, they ordered tea without milk whilst posing as working-class Brits. That would be seen as a little odd today. In the '40s and '50s, you may as well have turned up with a sandwich board saying, “I’m a spy.”
  • There are also many, many cases of German spies being picked up almost immediately after arriving in Britain, largely because the various feuding Nazi organisations' information was woefully out of date. In particular, they never seemed to grasp the intricacies of the British rationing system (for example, trying to pay for meals in restaurants with food ration tickets).
  • There were stories of British spies nearly getting caught for putting spoonfuls of soup straight into their mouths (in parts of France at the time it was customary for women to sip from the side of the spoon) and, of course, forgetting that the French drive on the right side of the road. Similar stories include (in this case, US) spies outed when they switch their fork from the left to right hand to eat, rather than the Continental style which keeps the fork in the left hand.
  • There's a true story about a suspected German spy being questioned for several days. The interrogators had their suspicions, but there was nothing definite, so they let the man go. He blurted out, "Danke..." The story is also told the other way around - an American spy, after days of interrogation, being told in German, "Well, seems you're not a spy after all, you can go" to which they replied - in English - "Thank you!"
  • And another one about two German spies entering a bar in USA and making the following exchange with the bartender:
    Spy: Two martinis, please.
    Bartender: Dry? (homophonic to German "drei" - "three")
    Spy: Nein, zwei!
  • And another one about German infiltrators during Battle of the Bulge:
    Spy (at American gas station): Petrol, please!
  • Whenever German spies infiltrated the Soviet army, they usually had perfect and impeccable histories, accents and documents. But the staples on their documents were shiny stainless steel — the USSR was still stuck with iron staples, which rusted.
  • Germans-dressed-as-Americans during the Battle of the Bulge were given away due to their forgers correcting an intentional spelling error on the standard GI identity cards.
  • American spies were supposedly outed by the Germans for crossing their legs the American way, by resting their ankle on the opposite knee. Europeans cross their legs by resting the back of one knee over the other.
  • Many a German spy was outed in World War II for failing to comprehend the mind-numbingly complicated British Imperial monetary system. Until 1971, the complex coinage, nonsensical divisions of currency (240 pennies to a pound, quarters of pennies, etc.), and numerous slang terms for the various denominations meant that merely counting change was extremely difficult for foreigners. This also nearly tripped up a sympathetic spy, Juan Pujol Garcia, a Spaniard who took it upon himself to feed false information to the Germans (and who was later inducted into the British spy network). Instead of trying to add up the totals on the fake expense accounts from his fake agents in the UK, he simply sent out itemized lists of things (like information) they had supposedly bought.
    • One of Pujol's fake reports claimed that in Glasgow (which Pujol never visited, being based in Lisbon during this time) there were men who "will do anything for a liter of wine". Not only do Scots mostly drink ale or whisky, they use the Imperial system of measurements, not the metric. Somehow the Nazis never noticed this. (Then again, selling wine in metric measurements is quite common, even in the US.)
  • Legend has it that the "Romeo" spies used by East German spymaster Markus Wolf to prey on lonely West German women who had access to relevant information eventually got compromised by German train conductors who noticed their totally unfashionable haircuts as soon as they entered West Germany.
  • Roger Bushell, the mastermind behind the famous WWII "Great Escape", and his traveling companion were captured in this way. The pair were pretending to be French, but an officer became suspicious and fired off a sudden question in English. Bushell's companion (who was actually from France and whose native tongue was French, but had grown accustomed to speaking English with his fellow POWs in the camp) instinctively responded in English as well. A fictionalized but relatively close version of the incident is depicted in the film version of the story (see entry under "Film").
  • Shibboleths are words that rely heavily on language-specific pronunciation. These have often been used to distinguish infiltrators from native speakers. Of course, they are useless against traitors.
    • The term itself comes from The Bible, in an account where, during a conflict between the Gileadites and Ephraimites in one of Israel's pre-monarchy civil wars, the Gileadites identified fleeing Ephraimites by their pronunciation of the word shibbólet (שִׁבֹּלֶת) (meaning "ear" in the sense of "ear of corn", i.e., "the part of a cereal plant that contains the grains"), which would have been pronounced sibbolet in the Ephraimite dialect.
    • The Dutch used the name of the port town Scheveningen to unmask Germans.
    • In 1302, during the Bruges Matins the Flemish used the phrase "Schild en Vriend" ("Shield and friend") to identify and murder French sympathizers.
    • In 1312, soldiers of the Polish duke (later king) Władysław Łokietek rooted out foreign members of a burgher revolt in Kraków by forcing every interrogated citizen to say "soczewica koło miele młyn" - a nonsensicalnote  string of Polish words, which were difficult to pronounce properly in fast succession by anyone not intimately familiar with the language. The city was summarily punished for the revolt anyway, but the foreigners identified this way received some extra attention.
  • Another WWII story tells of a soldier who tried very hard to pass as a civilian while in Europe. He got new clothes, a new hairstyle, learned the local language, etc. One day, while waiting on the curb with two bags of groceries in his hand, a German walks up and basically greets him with, "Hi, Soldier!" The reason? He had two bags of groceries in one hand, because the military ingrains the habit of keeping your other hand free to salute.
  • During WWII, German spies would often try to infiltrate Britain via neutral Spain, posing as Swiss businessmen in order to travel to Spain. The problem was, German standards of discipline were too high. German spies were under standing orders to stay sober, not frequent brothels, and absolutely not to deal on the black market, whereas given how expensive and heavily taxed cigarettes, sugar and other luxuries had become in Switzerland during World War Two, MI6 could tell with a good degree of accuracy who were real Swiss businessmen and who were spies simply by offering to sell them some cigarettes or nylons on the sly. At one point, the German intelligence services were receiving hundreds of reports from agents "in London" per month, all coming from agents caught and turned in Spain, writing fake reports from Barcelona using "The A-Z of London" and copies of The Times to keep their fake reports realistic. All because the spies were more honest in their dealings than the civilians.
  • An interview with early female CIA operatives suggested that women at the CIA were better at this than men. One now senior analyst stated, "You could always tell them by their socks." Another pointed out that regular Russian embassy employees always had cheap shoes, but the intelligence agents had very nice shoes.
  • This trope is Played for Laughs (in tandem with what appears to be either Political Overcorrectness or just Eagleland) in this Cold War-era joke:
    An elite American spy, after extensive and grueling preparation, is parachuted over Siberia in the dead of winter. He quickly gets rid of the parachute, dons local garment and starts to wade through the snow. After a lengthy march he finds a lonely hut, knocks at the door, and is allowed to enter by an elderly lady living in it. She invites him for a snack, and after some time asks:
    Lady: You're an American, aren't you?
    Spy: But Granny note , how could you?! Don't I speak like a Russian?
    Lady: You do!
    Spy: Am I not dressed like a Russian?
    Lady: You are!
    Spy: Don't I drink like a Russian?
    Lady: Oh, yes, you do indeed!
    Spy: Then why are you saying such things?!
    Lady: You see, son...it's because we have no Negroes.
  • This is how the Allies spotted Ernst Kaltenbrunner, the Nazi General in the SS. Kaltenbrunner gave himself up claiming to be a doctor and offering a false name. However, his mistress spotted him, and by chance occurrence, she called out his name and rushed to hug him. On 12 May 1945, this action tipped off the Allied troops, resulting in his capture, trial, and execution.
  • There are quite a few videos on YouTube of Phony Veterans like this one getting called out by actual soldiers for claiming to be part of nonexistent battalions or wearing medals improperly.
  • The English highwayman Dick Turpin was reportedly caught this way after fleeing to Yorkshire and changing his name. Dick wrote a letter to his family, but he'd been taught to write by a postman. So when that postman received the letter and realized 'John Palmer' had exactly the same handwriting as a notorious armed robber, the trail led back to Dick and he was arrested and executed.
  • One of the things that tipped off America that something was up in Cuba, ultimately leading to the missile crisis in 1962, was that Cuba started building soccer fields in high numbers. At the time, the sport of choice in Cuba was baseball - the Soviet Union preferred soccer.
  • A story goes that some WW2 American sentries used a line from the third stanza of "The Star-Spangled Banner" as a password, specifically "the terror of flight". Anyone answering "the gloom of the grave" was immediately arrested as a spy, because what real American knows the entire national anthem by heart?


 
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Leroy as Stitch

When Leroy disguises himself as Stitch after he has been captured, Lilo was able to tell he was an imposter because he was not wearing the tiki necklace she gave the real Stich prior to his departure.

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