->'''Yugo and Aki''': Who are you?\\
'''Keiji''': It's me, Tokiwa, yo!\\
'''Yugo''': What's 1+1?\\
'''Keiji''': 3!\\
'''Yugo''': It really is Tokiwa!
-->-- ''Manga/SilverSpoon''

In some cases where [[NeverSplitTheParty the party has been split]] or someone has changed so much you hardly recognize him or her, you may want to make sure the Bob in front of you is the person you know, and make some kind of check; for example by asking him something only the real Bob could know. But what to do when Bob is usually so [[TheDitz stupid]] he doesn't really know much? Well, you will check ''just that'' instead. Ask a question expecting an answer so silly that [[SomethingOnlyTheyWouldSay only the real Bob would be capable of pulling it off]]. Of course, Bob may also show his idiocy without waiting for any question. Inversely, giving an unusually intelligent answer will reveal the imposter.

Compare BluffTheImpostor. Will often overlap with SpotTheImposter.

SubTrope of SomethingOnlyTheyWouldSay. See also WhoWouldBeStupidEnough. Not to be confused with NobodysThatDumb.

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!! Examples:

[[foldercontrol]]

[[folder:Anime & Manga]]
* The above quote from ''Manga/SilverSpoon'' is after Keiji made a dubious relooking during his summer vacation.
* In the early volumes of ''Manga/{{Naruto}}'', anticipating a separation and knowing they are eavesdropped, Sasuke deliberately makes up a long, complicated password as a check. When Naruto comes back after they split up, he says the password flawlessly... which identifies him as an impostor since the real Naruto would have forgotten such a long phrase immediately...just as Sasuke thought he would. When the real Naruto shows back up, he announces that he forgot the password.
* In ''Anime/TanteiOperaMilkyHolmes'', Queen Claris attempts to prove to Milky Holmes and G4 that she's [[PrinceAndPauper actually someone else disguised as Sherlock]] by telling them a MouthfulOfPi. However, it turns out that she only has to say "3.14", before they're completely convinced that the person in front of them is way too smart to be Sherlock.
[[/folder]]

[[folder:Comic Books]]
* When the Stephanie Brown Comicbook/{{Batgirl|2009}}'s FriendOnTheForce gets in the middle of a fight between Batgirl and Clayface in Batgirl's shape, one of them says to shoot her, because she'll bleed and that will prove who she is. He shoots the other one, because only the real Steph could possibly think that was a plan.
* One WesternAnimation/DonaldDuck saw Donald getting arrested alongside a CriminalDoppelganger, a villainous GadgeteerGenius who used a homemade jetpack to rob a bank. To prove Donald's innocence, Huey, Dewey, and Louie suggests to the police to put him and the doppelgänger through an intelligence test. Donald visibly struggles with the test, while the doppelgänger aces it, leading the police to let Donald to go as he, quite a bit to his humiliation, simply was not clever enough to could have pulled off the heist.
[[/folder]]

[[folder:Film -- Live-Action]]
* In ''Film/TheWorldsEnd'', Gary repeatedly headbutts a pillar to show that he hasn't been replaced.
-->'''Andy:''' What does that prove?\\
'''Gary:''' It proves I'm human!\\
'''Steven:''' It proves you're stupid.\\
'''Gary:''' Exactly. OWWWWW!\\
'''Andy, Steven, and Peter:''' It's Gary.
[[/folder]]

[[folder:Literature]]

* In Literature/TheCulture novel ''Literature/{{Matter}}'' Farbin is a KingIncognito, one step ahead of the usurper who's declared him dead, who seeks help from his old tutor who hasn't seen him since he was a boy. The tutor says that if he's who he says he is, he'll remember the name of the tutor's assistant, and the subject of one of their lessons. When Farbin admits he can't recall either of these things, the tutor is reassured that this really is the UpperClassTwit he remembers.
* In ''Literature/TheRedTapeWar'', the cast has been subjected to a multi-player FreakyFridayFlip, and Marshmallow's father is trying to identify his daughter. He does this by asking her to spell "cat". The person currently inhabiting Marshmallow's body does so correctly. After another shuffle, he manages to identify the body his daughter is currently inhabiting by her utter inability to do so. Her version, to start with, involves a few extra letters.
[[/folder]]

[[folder:Live-Action TV]]
* ''Series/{{Blackadder}} II'': the MasterOfDisguise Prince Ludwig has infiltrated the court of [[UsefulNotes/ElizabethI Queen Elizabeth]]; the palace is having a fancy dress party to take her mind off her troubles and Blackadder (who was Ludwig's prisoner) told Ludwig that Nursie always dresses as a cow. Then Blackadder escapes, returns to London, and stabs Nursie while she's dressed as a cow - but it isn't Nursie, it's Prince Ludwig. Nursie's costume is then indeed shown to be horrendous.
-->'''Edmund:''' This was the information with which we bought our lives. We told him that, if the Queen was having a party, Nursie always goes as a cow. From that moment, he was doomed. All we had to do was escape, return, and kill the cow.\\
'''Queen:''' How could you be sure it was not Nursie?\\
'''Edmund:''' Because, My Lady, Ludwig was a master of disguise, whereas Nursie is a sad, insane old woman with an udder fixation. All we had to do was kill the one that looked like a cow. That was the mistake I knew that Ludwig would make. His disguise was too good.
* ''Series/ABlackLadySketchShow'': In "[[https://www.youtube.com/watch?v=MA6Zt0rNztM Plugged In]]," Omarion is faced with two women claiming to be his wife. In an attempt to SpotTheImposter, he asks how many O's are in his name. Both women answer "five" after much deliberation. He reveals that an incorrect response is the correct one for his purposes because his wife's math abilities are so poor.
-->'''Omarion:''' You're both wrong, okay? But my [=LaDonna=], she's horrible at math, okay, so ''actually'', you're both right.
* In ''Series/{{Eureka}}'', a computer simulation of Jack tries to kill Zane, only for the real Jack to show up moments later with no idea what just happened. Zane gets the drop on him and Jack frantically tries to explain how he came to be there and that it's really him. Zane believes him because "no computer simulation of you could be that incoherent."
-->'''Jack Carter''': Well in fairness you had a gun to my head.
-->'''Zane''':''(defensively)'' You were trying to kill me!
* ''Series/RedDwarf'': When a Psiren is impersonating Lister, the other characters ask one of the two indistinguishable Listers to prove he is the real one by playing the guitar. The first Lister does so, very well, and the other characters shoot him. They know the second Lister is the real one because he only ''thinks'' he can play.
* On the Israeli sitcom ''Shemesh'', the stereotypical DumbBlonde Ogen is revealed to be a spy, after a few characters notice [[ObliquelyObfuscatedOccupation they have no idea what her source of income is]]. She tries to go into [=HQ=], where she is asked for the password, and she answers, "...Can I get a hint?" She gets in, where she's told she's fired and can [[ObfuscatingStupidity drop the]] [[TheDitz ditzy]] act, [[BecomingTheMask but she has no clue what they're talking about]]. (Then again, this show has had a lot of NegativeContinuity, including Ogen's {{Backstory}}, which makes this a somewhat weird example.)
* A variation is used in the Mexican sitcom ''Series/ElChavoDelOcho''. Whenever someone utters the Spanish words for dumb, idiot, stupid etc., [[TheDitz Quiko]] would often come into frame and ask if someone is calling him.
* The first season of ''Series/TrueBlood'' revolved around a serial killer murder mystery. Secondary male protagonist Jason Stackhouse, widely known as a casanova but equally regarded as not the brightest bulb, is brought in by the police as the primary suspect, as he was documented as previously having sexual relations with most of the victims. When video evidence shows Jason actually in the coital act with one of the victims (including rough sex-style choking), it seems his goose is cooked. But when the rest of the tape is played and shows the victim very much alive and laughing, Jason exclaims this is proof he is innocent. One of the deputies nevertheless asserts that Jason might have come back later to murder the woman, and left the tape to throw suspicion off him, causing Jason to retort "I'm not that smart!" One shared look of acknowledgement by the officers and a scene later, Jason walks free.
[[/folder]]

[[folder:Video Games]]
* ''VideoGame/Persona4ArenaUltimax'': When faced with Kanji and Shadow Kanji and unable to tell the two apart, Yukiko holds an impromptu quiz show with questions about Inaba to determine which is the fake. Her last question is a math problem; when the Shadow gets it right, she proclaims he's the fake since the real Kanji would never be able to do the math so easily.
* In ''VideoGame/Splatoon2'', Marie wonders who's sending messages over her communication line with the player. She immediately identifies them as [[spoiler:her missing cousin, Callie]], when one of the audio transmissions somehow arrives upside down, a CallBack to the [[VideoGame/Splatoon1 previous game]].
[[/folder]]

[[folder:Webcomics]]
* ''Webcomic/{{xkcd}}'' has someone try to create a TrustPassword when a friend asks them to verify their identity over the phone before giving them a password, only for said friend to stop them mid-sentence because [[http://xkcd.com/1121/ only they'd suggest creating such a system on-the-fly over something more practical.]]
* ''Webcomic/SluggyFreelance'':
** In "It's the Wrong Torg, Grommit!" the protagonists have some issues with random dimensional travel, especially when parallel dimensions with parallel events start interacting. At the end, Riff and Zoë have to wonder whether the Torg who shows up through a dimensional portal is really their version of him. At first they think it's not, because he goes to [[KillerRabbit Bun-bun]] and asks for a hug. Then they realise it is, because he was using it as a test as to whether he was in the right dimension (only his Bun-bun would react so violently) -- and only ''their'' Torg would be dumb enough to use that as a test.
** In "Kesandru's Well":
---> '''Torg''': I was wrong. This house is not a ghost trap! It is an elevator to hell with ghosts in the gas tank.
---> '''Riff''': Elevators don't use gas tanks.
---> '''Torg''': Right... bad analogy. How about... It's an inverted toaster popping the bread of us on to the "two eggs up, and a side of bacon" plate of hell! ''With ghosts in the gas tank!!''
---> '''Riff''': Well, we know Torg's not possessed. That's Torg all right.
[[/folder]]

[[folder:Web Original]]
* A variation in the first campaign of ''WebVideo/CriticalRole'', where Grog knows ''exactly'' who has [[BerserkButton shaved off half of his beard]] the night before an important event, because only [[FearlessFool Vax]] would think it a good idea to do that to the gigantic goliath barbarian.
--> '''Grog:''' ''Vax.'' I didn't need to wake up to know it was you, motherfucker!\\
'''Vax:''' He's dumb as a post! Why does he know I did it?\\
'''Grog:''' Because you're the only ''fucking idiot'' stupid enough to do that!
[[/folder]]

[[folder:Western Animation]]
* The episode of ''WesternAnimation/FamilyGuy'' where Brian has to distinguish between the real Stewie and his evil clone - both are naked and there are no other clues. Brian is annoyed by having to play SpotTheImposter... but only because it's cliché and he already knows how to solve it: by asking them to look at their feet. The evil clone wonders why he'd ask this, while the real Stewie [[PingPongNaivete is captivated by his toes like the eighteen-month old toddler he is]].
* In an episode of ''WesternAnimation/GoofTroop'', Goofy encounters a criminal who looks just like him. In order to tell them apart, Max sets down a bucket of wallpaper paste and asks his real dad to please step forward. Max immediately knows that the one who manages to clumsily step in the bucket is Goofy.
* In an episode of ''WesternAnimation/InspectorGadget'', a criminal MasterOfDisguise infiltrates an important police meeting as Gadget himself. When the real one shows up, he accidentally knocks down Chief Quimby with his mallet, prompting Quimby to order the other one arrested.
* In an episode of ''WesternAnimation/ActionLeagueNow'', the Mayor creates an evil robot duplicate of [[DumbMuscle The Flesh]]. Since the other Action Leaguers are [[RuleOfFunny somehow]] unable to recognize the real Flesh as the one who ''doesn't'' have bolts sticking out of him, Stinky Diver manages to identify the real Flesh as the one who responds to his shout of "Hey, stupid!"
* On WesternAnimation/{{The Simpsons}} When Bart impersonates a Shelbyvillian, he is questioned by the other kids.
-->'''Shelbyville kid:''' How come we haven't seen you in school?\\
'''Bart:''' I don't go to school.\\
'''Shelbyville kid:''' Oh yeah? What's 2 plus 2?\\
'''Bart:''' 5.\\
'''Shelbyville kid:''' Story checks out.
* In ''WesternAnimation/SpongebobSquarepants'', when Sandy questions whether [=SpongeBob=] and Patrick were really them and not a [[ItMakesSenseInContext snail]], she asks Spongebob his mom's maiden name and [[TooDumbToLive Patrick]] his first name.
-->'''Patrick:''' Uh, is this a trick question?
* ''WesternAnimation/BooToYouTooWinnieThePooh'' had this. Piglet was trying to confirm that it was, in fact, Pooh. He suggested Pooh say something like, "I am Pooh." Pooh, naturally, said, "You are? Well, then, who am I?" Piglet chuckled and said, "It's Pooh."
* ''WesternAnimation/TeenageMutantNinjaTurtles1987'': When Bebop and Rocksteady meet some friends from before they were turned into mutants, they have to prove to their friends who they are. Rocksteady runs towards a wall and hits it with his head and it convinces their friends because they don't believe anybody other than Bebop and Rocksteady would do anything that stupid.
* In one episode of ''[[WesternAnimation/TwoStupidDogs Super Secret Secret Squirrel]]'', Morroco gets mixed up with his EvilTwin brother Shorroco. The two try to clam that they are Morroco by doing bumbling, clumsy antics, but Secret finally figures out which one is which by tossing a pair of valuable vases at them. Greedy Shorroco catches one while Morroco doesn't react fast enough and it hits him on the head.
* In an episode of ''WesternAnimation/JohnnyTest'', Dukey gets a cyborg clone of Johnny to reveal itself by asking a math question. The cyborg answers immediately with the correct answer, but gets blasted. When questioned why he blasted the one who gave the correct answer, Dukey points out he knew that the real Johnny wasn't smart enough to do math like that without counting on his fingers.
* Subverted in an episode of WesternAnimation/{{Bananaman}}, where an evil clone of Bananaman is created. The hero's resident NonHumanSidekick, Crow, has access to a device that can turn one of the two Bananamans into a banana, so he decides to test them with the trick question of "What's heavier, a ton of lead or a ton of feathers?" One of the two answers that both are the same weight, while the other replies "What kind of feathers?". Crow then zaps the latter, knowing that while the real Bananaman is a buffoon, he still is capable of successfully spotting such a trick question.
[[/folder]]
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