You Just Told Me



"Azula: So, I hear you've been to visit your Uncle Fatso in the prison tower. Zuko: That guard told you! Azula: No. You did. Just now."

- Avatar: The Last Airbender "The Headband"

Ben is undercover. Stan, typically a rival or enemy, knows or at least suspects as much; and tests his suspicion by blurting out Ben's real name. Inevitably, Ben will, quite unprofessionally, respond to the use of his name, confirming Stan's suspicions. Note that Ben's reaction is, in and of itself, sufficient to convict him, even if the two are alone and Stan could not possibly be addressing anyone else.

The trope operates independently of the good-bad alignment of either party.

The ploy used to force The Reveal need not be a name; it can be a specific word/phrase, or something spoken in the other character's native language. It can even be a non-verbal prompt, such as a familiar face, location, scent, etc. The point of the trope is that "Ben" is hiding something about himself, and "Stan" tricks "Ben" into revealing it by acting as if he already knows the truth, thus causing an automatic, unthinking reaction.

One of The Oldest Tricks in The Book.

Subtrope of Reflexive Response. See also Pull the Thread, Something They Would Never Say, Bluffing the Murderer. If Stan wasn't suspicious until Ben responded as Ben, it's Something Only They Would Say. If Stan says something that only an impostor wouldn't be suspicious of, it's Bluff the Impostor.

Anime and Manga
"Rivalz: [Lelouch]'s even holding a household account book... Lelouch: How do you know about that? Rivalz: Huh, you really do?"
 * In an episode of Yu-Gi-Oh!! series 0, a cop announces that a criminal has been tracked to the joint where Yugi and Jonouchi have gone for a burger, and their friends are working. The police sergeant says it might help that the crook is allergic to eggs; Anzu says (falsely) that he will be easy to catch, because the burger buns have lots of egg in them. At that, the crook freaks out and tries to bolt, despite having suffered no ill effects when he ate there the day before. In a subversion, this crook turned out to be a small-time shoplifter; the real perp did not fall for it.
 * Lord only knows how Little Kuriboh will spoof that scene when he comes to it...
 * In Death Note, Light Yagami of all people is once tripped up by this ploy, when Namikawa tells him that he already knows that  - it's only a very strong hypothesis at this point, but Light's surprised reaction is all the confirmation he needs. Of course, Light is.
 * At the end of the series, Light does this again.  Considering some of them were armed, Light was very nearly Too Dumb to Live.
 * Even Lelouch, The Chessmaster of Code Geass is not immune to these.

"Videl: So your identity is a secret, right? Saiyaman: Uh, yeah. That's correct... Videl: So, Gohan, how'd you get out of school? Saiyaman: Simple! I just said I was going to the bathroom and got here as...crap."
 * Detective Conan used this early on, with Ran and Conan.
 * The Novelization adds one of these to Gundam Seed. In the original series, when watching Kira fight, Andy quickly deduces that the Strike Gundam's pilot is a Coordinator. He later figures out that Kira is the pilot, most likely by watching his actions during a Blue Cosmos terrorist attack both are caught in. Realizing Kira is a both a Coordinator and not a native, and puts two and two together. He then confronts Kira in a scene which is played like he flat out knows what he is saying is true. In the novel, he suspects it (bases on his observations), but isn't quite sure, and uses one of these to confirm it.
 * This is how Videl figured out that Gohan was Saiyaman in the Dragonball Z manga.

"Roy: (being held at gunpoint) Lieutenant, what's the meaning of this? Riza: When we're alone, the Colonel always calls me 'Riza.' Envy: Shit! You two are-- Riza: Just kidding. Thanks for blowing your cover."
 * Used heroically in Mahou Sensei Negima. The Wild Card Kurt just finished a Hannibal Lecture, and made a sort of We Can Rule Together speech about saving "everyone," all 92 million of them- Negi then makes an educated, but still wild guess about what the disaster is, and Kurt, shocked, accidentally confirms it- and Negi points out that this confirmation has let loose the minor detail that Kurt's great plan for salvation is planning on abandoning 17/18ths of the planet.
 * Not quite sure how, but in Birdy the Mighty, Birdy says the trope line.
 * Riza pulls this on Envy in Fullmetal Alchemist.


 * When Ling is unsure if he's talking to the real Ed, or Envy is disguise, he dismissively calls him a pipsqueak. Ed responds as one would expect.
 * In Otome wa Boku ni Koishiteru, Sion started suspecting that Mizuho might be Wholesome Crossdresser pretty quickly, but she only confirmed it when - while passing Mizuho in the bathroom - she casually said "Your fly's undone." In Mizuho's defense, 'she' had only been acting like a girl for a few days by then. Later on, she gets so good at it that Sion actually forgets that 'she' is a boy sometimes...

Comic Books

 * Lucky Luke. The cowboys have captured a Native American and try to question him, but the prisoner apparently does not speak English. Lucky Luke serves him a glass of whiskey and asks him if he'd like some rocks on it. "No, thank you," answered the soon-to-be official interpreter.
 * Subverted in Knights of the Dinner Table: Brian's opponent in a naval wargame tries this, prompting Brian to "confirm" it by bursting out "How did you know that was my plan?." At the climax of the game, it is revealed that Brian had a different plan all along, and deliberately did this to mislead his opponent.

Fanfiction
"Once she was sure Nagato was out of earshot, Kiyoshimo leaned in close to the ferret and whispered "I know you can speak." Under her, the ferret visibly flinched, and then said, "I have no idea what you're talking about." Following that, there was a long moment of silence, the ferret having clamped its paws over his mouth."
 * More Things Involving Shipgirls That Are No Longer Allowed, Rule 2814

Film
"Ragnar: Stargrove! Lance: Is that name supposed to mean something? Ragnar: My mistake."
 * Famously used in The Great Escape when a couple of prisoners stop at the border. Eerything is going good well until one of the guards wishing them "good luck" in English, causing one of the prisoners to respond, "Thanks!" revealing himself as British. In real life, this was precisely how the leader and companion were caught. The trope is averted later in that film when another German attempts this on one of the escapees. He bluntly confronts the escapee with, "You are American!" but the escapee continues to feign ignorance and the German leaves.
 * Gene Simmons attempts this tactic against John Stamos in the movie Never Too Young To Die. In a subversion, Stamos manages to bluff his way out of the situation, though not convincingly:

"Austin Powers: Your boss, Number 2. I understand that cat's involved in big underground drills. Alotta Fagina: How did you know? Austin Powers: I didn't, baby. You just told me."
 * In Die Another Day, Bond uses this method to reveal the identity of Gustav Graves/Colonel Moon. The trope as played out here is somewhat less than effective, since the audience has already been alerted to this plot point.
 * In the Bond-wannabe film Agent for H.A.R.M., the lead character exposes the ersatz Bond girl as a villainous double agent by using her real name. The "even though they are alone in the room" clause, as stated above, applies here.
 * In Superman II, Lois tries this to reveal Clark's secret identity, first by calling him "Superman" and then by jumping into Niagara Falls. Naturally, Clark manages to rescue her without being obvious. In the restored cut, she tries jumping out a window, with the same result. Then she tries shooting him with a blank. Clark doesn't know that it's a blank, however, so he fesses up to being Superman.
 * Straightforward example in Who Is Cletis Tout Sloppy work on Finch's part to respond to his name, considering he was a fugitive in the middle of a room of cops.
 * In the 1993 adaptation of The Fugitive, U.S. Marshal Sam Gerard (Tommy Lee Jones) tricks fugitive surgeon Dr. Richard Kimble (Harrison Ford) into revealing himself when Gerard calls down a stairwell to a retreating figure, "RICHARD!" Kimble involuntarily looks up, giving himself away.
 * Subverted in the original script, in which Kimble does not look up when Gerard calls to him, even though other people in the stairway do. He does, however, freeze in place for a moment (no doubt stopping himself from reacting to the sound of his name), before continuing down the stairs at a visibly faster pace than before. The deliberate lack of response tips Gerard off just the same.
 * Exaggerated in Spies Like Us when Agent Millbarge suspects that a pair of agents supposedly sent to help him and his partner are actually KGB agents. He tells them a joke in Russian, causing them both to explode in laughter, saying "Da! Da!"
 * Austin Powers: International Man of Mystery


 * In this case Austin was aware of the fact ahead of time and was invoking this trope purely to look classy.
 * In Legally Blonde, a lawyer outs a witness as gay (to prove he couldn't have been the female defendant's lover), by asking him several rapid-fire innocuous questions (like "How long have you worked for her?" etc.), ending with "And your boyfriend's name is?" which the witness answers without thinking.
 * When he attempts to reestablish cover by claiming that he was confused by the rapid-fire way in which the questions were asked, and didn't realize he was being asked about a romantic boyfriend and that he's actually straight, his gay lover re-blows the cover by thinking he's telling the truth (since he is under oath, after all), and taking it badly.
 * And no one seems to consider he's bisexual.
 * Since being bisexual (supposedly) means that he would have been attracted to the protagonist.
 * In Mr. and Mrs. Smith, John, already suspicious about his wife, "accidentally" drops an open bottle of wine that she catches perfectly; then she realizes his ruse and lets it spill.
 * As with the above example, Crouching Tiger, Hidden Dragon also used this tactic. When Shu Lien suspected Jen was the thief, she purposely dropped a cup of tea on Jen, who instinctively caught it without spilling a drop.
 * In Billy Jack, Billy uses this ruse to trick Jean Roberts into revealing that she was raped by Bernard Posner. Don't ask what tipped him off, I don't know.
 * Fatal Instinct. Ned Ravine's secretary Laura Lincolnberry tells him that he has lipstick on his collar. He looks at his collar and says he doesn't. She says "You just told me" (if he hadn't been fooling around, he wouldn't have had to look at his collar).
 * Used in Men in Black, where Agent K finds out that an illegal immigrant is actually an alien because he cannot speak the native language of where he was supposedly from.
 * Well of course he's an alien, all immigrants are!
 * In All the President's Men, Woodward and Bernstein have a document identifying certain individuals only by the first initial of their surname. They believe "P" is a man named Porter, so while questioning a woman who may know, they casually intimate in a brief throwaway aside that they know "P" to be Porter. Her last words as they leave is an incredulous "How did you know about Porter?"
 * The two discuss the plan before they go and do it. Rarely, they discuss what happens if they're wrong. After a beat, they admit if that's the case, "We're screwed."
 * In Quantum of Solace, M calls CIA to ask about any ongoing operations in Bolivia. She gets transferred to Gregg Beam, who denies any operations. M then tells her subordinate that this proves the opposite, as there would be no need for the CIA Section Chief for South America to personally get this call otherwise.
 * In Where Eagles Dare, Nazi General Kramer is eventually convinced Schmidt is an ally and hands over a list of names of spies working in Britain, as well as confirming the identity of The Mole. Smith immediately reveals he had no evidence for this and the purpose of his mission was to extract the information from the Germans.

Literature
""So," said eyes wide but   laughter abating, "I suppose Bliss told you everything." "I haven't spoken to Bliss," said Julian. "Felton couldn't find him. All he found was this." He indicated the patchwork sack. "You mean- that's all you have?"  gaped at the sack. Laughter convulsed   again. 'You mean, if I'd only held my tongue- No, really, this is funny! It's an absolute screamer, don't you see? On the strength of a worm-eated pedlar's sack, I've put a rope around my neck."]"
 * Done subtly in The Fifth Elephant. The Patrician assigns Commander Vimes a manservant, Inigo Skimmer, for his trip to Uberwald. Vimes tosses an orange at him, and it bounces off. He doesn't say anything at that point, but later, when he reveals that he knew about Skimmer being a spy, he points out that a normal person would have either caught the orange or at least flinched (to confirm this theory, he later lobs one at Sergeant Stronginthearm, who ducks); Skimmer looked at it, recognized that it wasn't a threat, and let it go on its way, inadvertently showing that he has had assassin training.
 * Played with a bit in Night Watch too. Coates informs Vimes that "I know you're not the real John Keel." Vimes keeps a totally straight face, only to realize that that gave him away more thoroughly than anything he could have said.
 * Although in that case Coates didn't even need the confirmation, as he did actually know for a fact that Vimes wasn't the real Keel.
 * Also done at the end of the book, when Vetinari calls Commander Samuel Vimes
 * In Isaac Asimov's mystery novel A Whiff Of Death, the killer gives himself away by reacting to the detective grasping and starting to turn a valve that had been rigged to cause an explosion (the trap had previously been detected and neutralized).
 * In one of Asimov's short mystery stories, the culprit is a Québécois person using a false identity of an American. The detective tricks him into revealing his true identity by asking him to write the word "Montréal," and he writes it with an accent aigu on the e, whereas someone who only spoke English wouldn't spell it that way.
 * Alas, plenty of people who only speak English and who live near Montréal spell the name with the accent.
 * Another story involves the classic thrown object, with the twist that the perp is the thrower. He gives himself away as having spent a long time on the moon when he throws it far too short in normal gravity.
 * In a third Asimov story, "I'm In Marsport Without Hilda," a detective is trying to figure out which of several people in a room is a drug smuggler. All of the innocent suspects are currently loopy and speaking stream-of-consciousness gibberish, because they were given a drug to prevent space sickness, and the guilty party is faking it. Unable to figure out who is guilty, the detective, out of frustration, starts telling them about the hot date he would have had, if he wasn't stuck interviewing them. The guilty party's, um, "reaction", gives him away.
 * In The Robots of Dawn, Baley has circumstantial evidence against the criminal, who is unfortunately a very respected member of society (on another planet), so his word carries more weight than his. So, after presenting the evidence, he says the man might have committed something worse as a side effect. The criminal shouts there could have been no such side effect to what he did...
 * This is used a few times in the first book of Terry Goodkind's Sword of Truth series.
 * And then in the fourth, Kahlan appears to have learned the method - at least where girl talk is concerned.
 * In Stephen Fry's The Liar, the main character tries to hide his identity from the police, only to respond to his own name, which they got from the inside cover of a book he had with him. This is based on His Fryness's own experience.
 * Happens in Animorphs; Cassie (morphed as Rachel) is talking to a Controller, and he suspects her, so he randomly blurts out "Andalite!." If Cassie had reacted, she'd have given herself away, but she plays it cool and responds "Yeah, a light would be good too."
 * This is the modus operandi of Vlad and Kiera in the Dragaera novel Orca. They basically spend the whole book going around in various disguises talking to the conspirators, pretending to know more than they do (which is nothing) until they get a reaction, and then put all the pieces together.
 * In Iorich, the Empress thanks Vlad for his help in exposing a conspiracy in the East (detailed in the previous novel, Jhegaala). Vlad asks her how she knew he was the one who sent those anonymous letters, and the Empress replies that she didn't, until now.
 * Sherlock Holmes has used it at least once (in The Three Gables).
 * In Wicked, Elphaba pretends not to know Fiyero, and is a good enough actress not to respond to her name... but she does later respond to her childhood nickname, Fabala, while he chases her. It's kind of a moot point, though, as he was already sure it was her.
 * Egwene uses this in the latest Wheel of Time book. Black Ajah are the only Aes Sedai who can lie. She knows that a certain Aes Sedai is Black Ajah and needs to prove it to the rest. She asks her a rapid-fire series of questions, to which any Aes Sedai would give vehement denials. ("Do you consort with the Forsaken?" "Do you serve the Dark One?") Then she asks a question about her target's hair color. Her target denies her own hair color, which proves to the assembled audience that she is Black.
 * All Aes Sedai are required to swear a magically binding oath to not speak any word that is not true. They literally choke up any time they are about to actually lie. (Though they are masters of distorting and twisting meanings).
 * Also used by Lady Dyelin to Birgitte. It's implied that this has happened multiple times offscreen as well as the onscreen times. In the onscreen times, Birgitte handles herself well.
 * Mark Twain's The Adventures of Huckleberry Finn. While Huck is wearing a dress and pretending to be a girl, a woman determines he's actually a boy by tossing a lump of lead into his lap. He clasps his legs together to catch it, the way a boy wearing pants would do, instead of spreading his legs apart, the way a girl wearing a dress would do it.
 * Kaladin proves his suspicions that Teft was once a squadleader using this method in The Way of Kings.
 * In St. Elmo's Fire, Alec replies "What did Kevin tell you?" after his girlfriend asks him about his "extracurricular love life" and beats on Kevin in retaliation. Kevin hadn't spilled a thing; his girlfriend just had a hunch.
 * 19th-century amateur detective Julian Kestrel uses this in his first novel Cut to the Quick

"Han: "What makes you think the Empire's involved?" Ferrier: "With Grand Admiral Thrawn in charge over there? He's involved in everything." Han: "Thrawn, huh? Thanks, Ferrier.""
 * In the last book of the Codex Alera, Tavi and several members of his high command are on a ship under attack by Vord scouts. Magnus has been suspicious of for several books, since he seems to know a little too much about espionage for a decorated soldier, . So, at the very end of the fight, he shouts, "! Behind you!,"  Tavi, who had agreed to the plan thinking it would exonerate his loyal subordinate, is very, very angry when  immediately whirls around.
 * * In Trickster's Choice, Aly mentions weapons in hidden storerooms under the stables. Lokeij says he has the stables watched all the time, and there's no way Aly could have known about them. Aly replies "I didn't know until now."
 * In I, Jedi, Corran Horn goes undercover as Keiran while training at Luke Skywalker's Jedi academy, changing his name since he's a mildly famous pilot. Interestingly, after leaving the academy "Keiran," going by yet another name, is questioned about Luke. He goes on to display an appalling lack of knowledge about one of the single most famous and important people in the galaxy in order to keep up the ruse.
 * In Dark Force Rising, when Mara Jade, a former assassin for Emperor Palpatine, meets with Grand Admiral Thrawn, he says "Come closer, Mara Jade." (The two had met several years before and she was under an assumed name). She begins instinctively walking forward, catches herself and comments that Thrawn shouldn't have to rely on such cheap tricks to verify who she was. He agrees, and then asks her questions that only she would know the answer to.
 * Used again in the same book. No one in the New Republic knows the name of the new Grand Admiral on the scene. Han Solo meets with a ship thief who does know, and is offering to show Han the location of a lost fleet before the Empire finds it.

"Anduin: I don't mind. But then again, I don't have secret meetings with orcs in the middle of nowhere. Jaina: How did-- Anduin: Yes! I was right! You were out meeting Thrall!"
 * In Zahn's Outbound Flight, Thrawn is able to get an awful lot of information out of a Corellian guest/prisoner who really doesn't want to tell him these things by working this method into conversation, though he makes it look effortless and never actually says the trope name.
 * In Sir Walter Scott's The Monastery, the courtier Sir Piercie Shafton, who speaks in high-flown Euphuist terms, is disguised as a milk-maid; questioned as to who he is, he replies, "I am she, O most bucolical juvenal, under whose charge are placed the milky mothers of the herd." His disguise is unsuccessful.
 * In Christie Golden's World of Warcraft: The Shattering, Anduin Wrynn deduces that Jaina Proudmoore has been meeting with Thrall in this manner.

"The maid: How did you guess? Volha: I didn't. You are the sixth one I told this. Others just thought me crazy."
 * In the Doctor Who Expanded Universe short story "Walkin' City Blues", the Doctor bursts into the Big Bad's office and announces he's seeking justice for Boko Berikuka. When the man launches into a rehearsed speil about "Boko Berikuka" being a meaningless phrase used by the citizenry, the Doctor points out an innocent man would have called the police, not tried to dodge a question that hadn't actually been asked.
 * In Belorussian writer Olga Gromyko's Witch cycle, the titular witch Volha once uses this trick to find the shapeshifting monster natsyga. It becomes known that the natsyga hides among the castle servants. Volha tells one of the maids: "Why don't you assume your real shape?"

"Caine: Fuckin' amateur."
 * In M. K. Wren's Phoenix Legacy trilogy, Val Severin finds new Phoenix member Alex Ransom looking up some information relating to the fallen Peladeen Republic ... and the fact that the missing and presumed dead heir of the Peladeen Lord had the same name as one of the Phoenix Councilors. Shocked, Val asks how much Alex has been told about "the Peladeen Alternative"; it's top secret. Alex smiles and admits that all he knows is that the Councilor in question is key to the Peladeen Alternative. He never gets around to telling Val that he hadn't even heard that term until she blurted it out.
 * In the third book of The Acts of Caine, Caine meets a spy for an old friend of his, and instructs the spy to take a message to her. The spy plays dumb for a while, until Caine offers to explain what gave to spy away (so that he can correct the mistake). The spy admits it would be useful to know how Caine was so sure. Caine just says "I wasn't sure."


 * In The Elric Saga, this is how Elric finds out that.
 * One Flew Over the Cuckoo's Nest: McMurphy runs through the hallways of the asylum warning the patients that an orderly is on their way to check on them. Everyone stops what they're doing and pretends to sleep, including Chief Bromden, the narrator. After it turns out to be a false alarm, McMurphy casually says to Bromden, "Hey Chief, I could've sworn they told me you was deaf!" Bromden had been pretending to be deaf and mute for years before McMurphyshowed up.

Live Action TV
"Eliot: Is this a patient of yours? [shows picture of suspect] Psychiatrist: I am not at liberty to say. Eliot: You just did. Confidentiality only applies to patients."
 * Shows up in Law and Order SVU:

"Elaine: Hey, George. Did you buy that sweater, knowing the red dot was on it because you could get it at a discount? (bluffing) Jerry told me that you did. George: (Turning to Jerry) You told her?! How could you tell her? What kind of friend are you? Jerry: I didn't tell her, you stupid idiot! She tricked you!"
 * Which is completely ridiculous, because that's the answer any psychiatrist with half a brain would give regardless of whether or not they even recognized the person. They cannot confirm or deny. A neutral answer is the only thing that a psychiatrist—or any physician—should ever give.
 * Law and Order UK: The detectives have arrived at a junkyard to look for a murder suspect. The supervisor denies that he's there. Suspecting otherwise, DS Devlin very casually calls out, "Oi, Freddy!" Sure enough, the "Freddy" in question looks up, then further confirms his identity by bolting when he sees the cops.
 * The series Knight Rider did this numerous times. On one occasion, a woman impersonated her recently murdered mother to flush out the killer; on another, a blind woman pretended to drive, suggesting to the criminals that she might have witnessed their deeds.
 * Michael Westen on Burn Notice pulls a scheme called a "reverse interrogation," in which he lets the criminal interrogate him, and hopes the bad guy will give away important information in his questions. (He does.)
 * Elaine pulls this trick on George in "The Red Dot" episode of Seinfeld.

"Elaine: Did you leave that drink by Dick on purpose, knowing he's an alcoholic? Jerry: Absolutely not. Elaine: (bluffing) Really? Because George said that you did. Jerry: Nice try."
 * She tries it again on Jerry in that same episode, but he sees through it.

"Doakes: That's all you care about, is your job. Even if it meant doin' Pascal's man to get it back. LaGuerta: How did you know about Bertrand? Doakes: I didn't for sure until just now."
 * A nice subversion in this case, as Jerry is telling the truth.
 * Angel, "Blind Date": Angel throws an object at a woman claiming to be perfectly blind; she catches it out of the air perfectly. Oops.
 * Of course, she actually is completely blind, and he knows it... the point is how the court full of people react to this.
 * In an episode of The Agency, an undercover agent has replaced a person who's known to be allergic to dogs, so he reacts accordingly whenever there's a dog in the room. He's discovered when his suspicious contact places a dog nearby but out of sight and he fails to develop a stuffy nose.
 * In one episode of Monk, the identity of a mail bomber is confirmed when he panics at the sight of someone opening one of his custom-made packages. He shouldn't have known about the bombings because he had been in a coma when they took place. (If you're curious about how he managed to set off the bombings while in a coma, watch the episode in full). In another episode, he cleared Willie Nelson's name by proving that the other suspect wasn't blind (or at least, not completely blind)--he had a streaker run past her, and she reacted.
 * In yet another episode, the murderer had to make sure that his wife's corpse was found without revealing that he had killed her, so he Monk trapped him by
 * From Dexter:

"Airman: Vy sovetskie shpiony? Daniel: Nyet! O'Neill: Daniel? Daniel: He just asked if we were Soviet spies, I... O'Neill: [glares] Daniel: Um."
 * In the Mash episode "Out of sight, out of mind," Hawkeye gets blinded by an exploding camp stove; and goes to sit in a nurses' tent for a while (why, I don't recall). One of them is cautious about undressing with a man in the tent, even if he can't see her. At the end,, he wraps his head back up again and goes back into the same tent, tells them he has had a relapse, and suggests that they would be perfectly safe undressing. One of them promptly throws a hairbrush (or maybe a mug) at him, which he catches perfectly; and they throw him out of the tent with some alacrity.
 * An earlier episode had a rash of thefts occur in the 4077th, with the stolen articles found in Hawkeye's footlocker. To catch the real thief, Hawkeye gathers all the "suspects" (everyone who had something stolen, or simply held a grudge against Hawkeye) to the mess hall, where he says he coated his footlocker in a time release chemical that would turn the thief's fingernails blue. The culprit turns out to be
 * The Mentalist - Patrick Jane and the team encounter a hooker who seems to know only Chinese, but when Jane comments on an imaginary hideous thing on her shoulder, she nearly jumps out of her skin. Busted.
 * Stargate SG-1: This trope is used and parodied in the episode "1969." The team is stranded in a top-secret Air Force facility in 1969, and are suspected of being spies. An Air Force interrogator comes in:

"Penny: Why did you take that girl home? Vince: (sigh) Who told you? Penny: (sadly) You just did."
 * In another episode, when preparing to give the Aschen some stargate codes, Samantha Carter then asks one of the Aschen what a particular word means. The Aschen, not realizing the repercussions of what would happen, simply answered "sterility," in essence admitting that the drug they were giving the Tau'ri would actually give them sterility, making quite clear of the Aschen's ill-intentions towards Earth.
 * Used in Just Good Friends where Vince has been unfaithful to Penny. Again.

"Officer: [Latin] Right, be off with you. (turns away) [Egyptian] Please bless us with your forgiveness, sacred majesty. "Greek slave": [Egyptian] Granted, mortal. (beat) (fight scene)"
 * In the Lost episode "The Cost of Living," Jack has seen x-rays and believes they are Ben's, so he questions him about symptoms. Ben's reaction gives him away. Later he asks Juliet why she told Jack about his tumor, to which Juliet replies that she didn't; Ben did.
 * On House, Foreman finds out about Thirteen's bisexuality this way.
 * Earlier in the series, House is talking to an 18-year old kid who is taking care of his mother. He later puts an X-ray on the lightboard, and says he can tell the person is about 15. The kid confesses to lying about his age. After a brief conversation, House reveals that it wasn't even the kid's X-ray.
 * Subverted in an episode of Quantum Leap where Sam leaps into the body of a blind musician, and maintains his sight. A woman becomes suspicious, thinking that the man had never been blind, but when she tries to out him by flicking a lighter in front of his face, he can't see it because he had just been temporarily blinded by a camera flash.
 * A similar, more painful, subversion occurs on an episode of Arrested Development. Michael tries to prove a blind woman is only faking her condition by throwing a book at her. Unfortunately, she's been temporarily blinded for real and the book hits her in the face.
 * In Rome, this happens in a manhunt for Cleopatra's son.

"Odo: In that case, why are you working on your acceptance speech? Bashir: (Hides pad) How did you know? Odo: (smugly) Just a guess."
 * In this same series, Atia uses this tactic to expose Octavia's relationship with Agrippa.
 * In one episode of the sketch show Smack the Pony, two women and one man are being held hostage alone in a room somewhere. One of the women tells the others that her name is some male one. This puzzles the second woman and she keeps asking for explanations for it, but the other just maintains it just is that way. Eventually we see the second woman whispering the other various female names while she sleeps, until she reacts to one and has to admit that was her real name all along; she was just fooling the others as a joke.
 * The bad guys tried this quite frequently on Mission: Impossible, but one notable case had a gangster see Rollin (playing a deaf waiter) react slightly when a large amount of money was mentioned. In order to test the him, the gangster fires off a revolver next to his ear. Rollin fakes not hearing it, passes the test, and reacts in agony at the pain when he gets out of sight.
 * Another episode had the team infiltrating a camp where foreign agents were being trained to pass as Americans. Rollin intentionally blows one such test to prove he's a "genuine" newbie who wouldn't know how Americans would act.
 * And in yet another, he catches a glass vase abruptly tossed at him by a foreign spy, who knows the spy Rollin is impersonating is left handed.
 * In Star Trek: Deep Space Nine, Dr Bashir is up for a major medical award. He insists that there is no chance of victory for him, and so he does not wish to discuss it.

"Elaina: I'm asking you. Elaina: It should, : How did you know? Elaina: I wasn't sure, now I know"
 * One Bones episode ends with her offering everybody in the victim's funeral a cup of tea "from his own private stash. The same that was his last drink."
 * In an early episode of Merlin, Gaius is certain Merlin is a wizard, but wants to see it for himself. He "accidentally" knocks a pitcher of water off the table, causing Merlin to react by using magic to freeze the pitcher in mid-air. When Merlin realizes what he's done (as he was explicitly warned not to use magic in Camelot, where it is banned), he releases the pitcher, but not before Gaius points out that stunts like that would blow his cover very quickly.
 * Used by Elaina in The Vampire Diaries
 * That doesn't mean anything to me.

"Jack: Oh. Oh, I know. I know what this is. Will told me everything. Grace, you really did it this time! Grace: (to Will) You told him I slept with Rob?! Will: Uh, no. Jack: Works every time."
 * Ricky does this to Ben in The Secret Life of the American Teenager when asking Ben if he had been to see Adrian.
 * In an episode of CSI, a suspect is confronted with a briefcase that resembles one owned by his victim. Thinking it's the same case, he protests that they're not allowed to break into his car, and the investigators thank him for telling them where to look for the real one.
 * Used by Sheriff Deputy Andy the robot in Eureka to confirm that Sheriff Carter and the others had, in fact,
 * Hogan's Heroes: The gang's always careful about their captors setting up a plant in their barracks. In one episode they decide to test a new American "guest." In the middle of the night, they all start making noise and shouting "FIRE!" - Kinch yells at him, in German, "Quick! Out the window!" Newbie heads straight for the window.
 * Used once on NCIS when they had a suspect who refused to tell them who he was or which country he came from. They had Ziva speak to him in all the different languages she speaks, and when he stared blankly at her the whole time except for a visible reaction when she spoke Russian, they knew that he was from Russia.
 * The second season of Oz begins in the aftermath of a prison riot, with an investigator trying to find out how a prisoner was shot by a weapon that was reported missing and then later was returned to the prison armory without explanation. Near the end of the episode, the investigator confronts a suspect and lays out an explanation of how it could have happened, and hwy that suspect covered for someone else caught in the riot. Eventually the suspect grudgingly asks "Who told you all that?" Three guesses what the response is.
 * This priceless exchange from Will and Grace:

"Byron: Last NIGHT? Dwayne: You didn't know. Byron: No, I didn't. You Just Told Me."
 * On an episode of A Different World, Whitley's new boyfriend Byron has noticed the tension between Dwayne and Whitley and asks him about it. Unfortunately, in doing so, he learns more than ever expected to—Dwayne confirms Byron's suspicions that he and Whitley had previously been involved, but assures him that the relationship is over and that "Last night was a mistake and it meant nothing".

"Kensi: How did you know that I.. Deeks: I do now!"
 * Subverted in the "Who are you" episode of ''Buffy the Vampire Slayer. After Buffy swaps bodies with her Evil Counterpart Faith, Buffy is apprehended by the police and Faith remains alone with Buffy's mother Joyce. The first thing Joyce says is "Faith", and the changeling indeed reacts involuntarily, so it does looks like Joyce deducted her true identity. However, it turns out she didn't and is just willing to ask "Buffy" about Faith.
 * NCIS: Los Angeles: Deeks does this to Kensi by commenting he didn't see a phobia she'd just mentioned on her online dating profile.

"Linden: Oh, and councilman, you might want to call off your dog at the school. He won't find anything. Richmond: And how did you know about him? Linden: I was guessing. Richmond: And I just confirmed it."
 * In the pilot of the American version of The Killing, Detective Linden pulls one of these on Councilman Richmond:

"Mr. Schue: Wait, who gave you these questions to ask me? Brittany: Coach Sylvester says I'm not at liberty to say."
 * The Nanny: Fran does one of these to C.C. in "Where's the Pearls?" when she guesses that she and Maxwell are trying to keep her away from a celebrity. She's right: it's Elizabeth Taylor!
 * From Glee:


 * In Scrubs, Turk eventually tricks Carla's brother into speaking English in front of her (she thought he only knew Spanish) by saying explicitly sexual things about Carla in front of him.
 * Boy Meets World: When Mr. Feeny asks Frankie Stechino whose idea it was to force Cory and Shawn to dress as cheerleaders, Frankie responds: "I cannot say. I must protect my friend Joey the Rat." Oh, and by the way,.
 * In the Green Wing episode "Rumours", while trying to persuade Guy Secretan to deny the rumours that they slept together, Caroline Todd tells him that she knows something embarrassing about him. He hurriedly denies the rumor that Sue White has penetrated him anally, which Caroline had not in fact heard.
 * In the Criminal Minds episode "Bloodline", Hotch and Prentiss are doing the Good Cop, Bad Cop routinue to try and get the name of a person out of the perp. Hotch then reads off a list of their suspects. The perp reacted at one of the names and shouts "I won't tell you!" and Hotch replies "You just did". The Oh Crap look is priceless.

Video Games
"Eggman: You thought you could trick me with that fake Emerald, didn't you? Tails: So... how did you know it wasn't the real one? Sonic: (cutting him off) TAILS! Eggman: Because you just TOLD me, fox-boy!"
 * In Uncharted 3, Marlowe tells Nate Drake that she knows where Ubar is because 'you told us, Nathan.' while he was under the influence of a Truth Serum.
 * In Sonic Adventure 2, Dr. Eggman uses this ploy to confirm that he correctly guessed which of the two identical-looking Emeralds is the real one.

"Heather: So! You're the ones sent by Ludveck of Felirae?! You've been stirring up these little revolts all over the place! Yeardley: What?! How did you know?! Heather: I see things here and there. But half of it was just a guess! ...Judging by your reaction, though, it seems I was right."
 * In the third case of Phoenix Wright: Ace Attorney: Trials and Tribulations,
 * Or if
 * Unlikely, as
 * Used in Fire Emblem Radiant Dawn. Heather, a small time thief, confronts Yeardley, a general working on Duke Ludveck's orders, about his attempts to get the townspeople of Crimea to revolt against Elincia.

"Marcia: ...I think I see. You owe them money, don't you? Isn't that the real reason why you don't want to see them, cheese breath? Makalov: W-when did you learn to read minds like the herons!? Marcia: I can't, you spineless sea cucumber! It's just so typical of you that I guessed!"
 * Later on, when Marcia confronts her useless brother Malakov as he tries to avoid fighting Imperial Army troops:

"Axel: Don't forget. Sora is the key. We need him if we're going to take over the Organization. Larxene: I know that you're in on it too, but keep it under your hood. At least until the time is right. Axel: *after Larxene leaves the room* You would have been wise to do the same, Larxene."
 * A variant where "Stan" doesn't let "Ben" know when he figures it out. In Kingdom Hearts: Chain of Memories, Axel is sent to Castle Oblivion because Marluxia and Larxene are suspected of plotting against the Organization. About halfway through the game, Axel chats with Larxene about the plan they have for Sora as Larxene heads down to meet Sora.

"Viktor: You're Tesla, the Scrivener, right? Albert: Goodness, no. My name is Albert Onyx. My people have lived here for generations. Viktor: Really? Then what is your mother's name? Albert: Ummm, her name is Marianne Onyx. Viktor: And your father? Albert: I believe it was... Ah... Allen Onyx. Viktor: Grandmother! Albert: Uhh... let's see... Leah Onyx. Viktor: Hey Tesla. Albert: Yes? Albert: .............! Albert: I mean... that's not my name, Tesla. Viktor: Do you give up? Tesla: All right. Mathiu wants me, right? I prefer to lead a quiet life. Viktor: Stop yapping and get ready to leave Tesla: O-OK. My god, how unlucky I am. Tesla: Led back into a life of crime. *Tesla joins*"
 * In Suikoden Viktor uses this on Tesla in order to recruit him since Tesla just wants to live a quite and simple life and pretends to be Albert Onyx. The party already learned that he will pretend to be Albert from Kimberly before visiting him.

Web Comics
"Helen: You know I'm not "Dave Pretorius." There's no such man. You know I'm really your own daughter in disguise. You know I infiltrated D-Con to crack the Dave Conspiracy, having no idea you'd already done it! ...And you didn't actually know any of this until I voluntarily told you, did you? Dr. Narbon: I'm such a great mother."
 * A creative application of the trope occurred in Rip and Teri. Agent XI knows Rip has infiltrated a TV studio in disguise. A few days earlier, Rip had encountered XI in a janitor uniform, so XI stations himself inside the studio in the same uniform. Rip's startled reaction to seeing the same "janitor" he fought earlier gives him away.
 * From Narbonic, during the D-Con Story Arc:

"Bigs: (thinks) If you are trying to read my mind I swear I will deck you. Dan: Huh? How would you know that I-- Pow!"
 * Cleverly done in Dan and Mab's Furry Adventures:

"Case: But...but...How did you know that? Snow: I only had suspicions, but you just confirmed them!"
 * Used in Eight Bit Theater here.
 * In this Krakow comic, Canadian rap sensation Snow tricks one of the characters into admitting that he altered the lyrics while singing one of Snow's songs.

"Murtaugh: Your engineering skills are way above your pay grade. Sorlie: Actually I only put it together a minute ago. Then I guessed, and you confirmed it. Flinders: Your intel skills are way above your pay grade."
 * In Two Evil Scientists, Eggman Nega invokes it here when he's confronting his ancestor
 * In this Everyday Heroes episode, Mr. Mighty finds out about a planned crime. It works so well, he tries it again on the next page.
 * A priest in Nukees confirms Gav is a lapsed Catholic by saying "peace be with you" as he leaves, getting an automatic "and also with you."
 * In Exterminatus Now Steve effortlessly got Virus to confirm that the group visiting Cesspool is from Inquisition. Of course the old skunk ruled a bar/employment agency for unruly mercenaries/Black Market spot for many years, so it's kind of expectable that in such situations his brain is in working order.
 * Schlock Mercenary had Haley Sorlie, an UNS shipbuilding specialist temporarily used as a "cultural attache" (overt and sort-of-invited spy) and field-promoted to captain in an emergency, figure out that Toughs are lugging around a variant of the weapon as much as possibility of which is unknown to pretty much everyone except the old owners of an experimental piece (UNS military), its new owner (rogue AI), the new owner of the ancient one (Oafa), Fleetmind and Toughs who have seen it while working for all of the above (which could badly affect their expected lifespan, but they stumbled upon nastier secrets anyway). While her mental processes were overclocked to "frantic" via being in a city about to get either vaporized or flattened. A moment of awkward silence ensues. Two pages later -

Web Original
"Sandra: I could believe this stupid shit from Mike, but I never thought I'd catch you Simon: ...What? Sandra: You heard me! Simon: Christ, does everyone know about it by now? How long have you known? Sandra: Known for sure? For about-- (checks watch) --ten seconds. Simon: Oh Jesus, I walked right into that, didn't I?"
 * In High Fidelity, after Simon tells Sandra that :


 * In the new season of The Guild, this is how Codex admits to.

Western Animation
"Dib: Zim! What are you doing here? Zim: I am infecting this city with genetically enhanced vermin, but you'll never know! Dib: You just told me. Zim: (after a brief pause) "You're LYING!"
 * In Disney's Aladdin, Jasmine, suspecting "Prince Ali" to be Aladdin, idly mentions Aladdin's friend/pet Abu (whom "Ali" would not know about); Aladdin responds without thinking.
 * The Iron Giant: Annie Hughes is talking to junkyard owner Dean McCoppin. She mentions Hogarth (her son) sneaking out to the junkyard, and he asks if she knew about it, and she says "I do now."
 * In Iron Man: Armored Adventures, Pepper has a hunch that Tony Stark is Iron Man, so she confronts him about it and he casually asks how she figured it out. You Just Told Me. Though in his defense she did give him some good reasons that he believed she already knew, she was practically just confirming it by this point.
 * As the page quote shows, Azula in Avatar: The Last Airbender uses this to trick Zuko out, not about his idenity, but about visiting his Uncle Iroh.
 * In Daria, a Dream Sequence that parodies Murder, She Wrote has Daria investigating the murder of Kevin, that she's been framed for. She says that she coated her locker (where the murder weapon was planted) with a clear paint that changes color over time, and the hands of whoever was in her locker would be turning pink any minute. Three suspects check their hands, then she says she made the whole thing up since only the guilty party would look.
 * Parodied in Invader Zim episode "Mortos the Soul Stealer"


 * Doug: A douchebag student named Willy claims his teacher is incompetent and tries to get her fired. In front of an assembly, Doug asks Willy questions about classic novels, mangling the details along the way. Willy smugly corrects Doug at every turn...but Doug points out that he and Willy learned all of that stuff in the teacher's class, so she has to be decent at her job. Willy has no choice but to drop his suit.
 * This clip from The Batman.

Real Life

 * Shouting "Attention!" is one method of revealing if someone has military training (an FBI agent did this while interrogating a suspect in the 1998 Nairobi bombing). Shouting "Achtung!" unexpectedly was used among Allied prisoners of war to uncover German infiltrators.
 * To tell if someone speaks a language or not, police often ask them to say what color different words are (like the word "red" written in green ink). People who speak the language will take far longer. This is because this is the Stroop Test, a psychology tool in which taking longer is normal, under normal conditions.
 * A Russian proverbial story tells about a guy who spots a pickpocket in the market. Nobody else seems to do, so the quickwitted fellow shouts: "The thief has his hat on fire!." The crook instinctively grabs his headgear.
 * Very similarly, in a Serbian folk tale, St. Sava (the man that established the Serbian Orthodox Church) was asked to use his wisdom to find a thief in a crowd. He replied with "Oh, that's easy. It's the guy with the bee on his hat!" pointing out into the crowd's general direction. Of course, the guy waves his hand to chase off the (nonexistant) bee, and gets caught.
 * A lateral thinking puzzle asks how police putting up signs warning about pickpockets actually helps the thieves. The solution is that
 * Alternatively, an old trick amongst pickpockets working in groups is to have one person turn to a friend and (loudly) proclaim "Somebody stole my wallet!" The marks nearby instantly will pat their own wallets, broadcasting the location of their valuables.
 * One TV show about scams showed that thieves sometimes take advantage of this and put up the signs themselves!
 * Undercover police officers usually use their own first name to avoid this.
 * To avoid this, while agents were in training they would be woken up by instructors in the middle of the night and asked things like "what is your mother's maiden name". The other point was so they would know their cover story so well it may as well have been their own life.
 * A member of Allied intelligence in World War Two thought agents were captured and impersonated, so at the end of one of the messages he sent H.H. (for Heil Hitler) the message he got back from the 'agents' also ended in H.H.
 * A preteen/teenager joke in Brazil is saying "The hands of whoever just farted are yellow". Whoever looks...