[[quoteright:350:[[Film/{{Superbad}} http://static.tvtropes.org/pmwiki/pub/images/mclovin_fake_id_hawaii_11.jpg]]]]
[[caption-width-right:350:"Alright, you look like a future pedophile in this picture, No. 1, No. 2: It doesn't even have a first name, it just says ''[=McLovin=]''!"]]

->'''Homer''': Hello, my name is Mr. Burns. I believe you have a letter for me.\\
'''Postal Worker''': Okay Mr. Burns, what's your first name?\\
'''Homer''': ''[beat]'' ...I don't know!
-->-- ''WesternAnimation/TheSimpsons'', [[Recap/TheSimpsonsS2E22BloodFeud "Blood Feud"]]

This trope is when a character, in disguise or otherwise pretending to be someone else, doesn't know some basic piece of information about the person they're pretending to be. This could be because they didn't research the identity enough, or maybe the disguise and cover identity were done in a rush and they didn't think all the way through.

A quick-thinking character might be able to bluff their way out of the situation, either through a LineOfSightName, using their RealNameAsAnAlias, or simply pulling the BavarianFireDrill. This can backfire if they [[OutOfCharacterAlert say the wrong thing]], mess up the TrustPassword, or if the person they're trying to fool is [[BluffTheImpostor already suspicious]]. Otherwise, HilarityEnsues as the character either tries to play it straight (i.e., they've [[TooDumbToLive somehow ''forgotten'']] their first name, birthdate, hometown, etc...) or just tries to [[TheExitIsThatWay awkwardly escape]]. In drama, this might lead to a tense situation where the character is found out and has to escape without being caught.

Compare StereoFibbing, for when two characters have to make up a lie on the spot to get out of this situation.

See also ImposterForgotOneDetail and SpottingTheThread.



[[folder: AnimeAndManga]]
* ''Manga/KamenNoMaidGuy'' has an example where the twenty-something NinjaMaid Tsurara tried to infiltrate Naeka's school as a student. The usually ditzy Naeka asked her which EasternZodiac year is her birthday in. For people in heavily Chinese-influenced country, your own zodiac year is something you already know and and can be answered without thinking. Calculating your supposed birth year from a fake age and come up with zodiac year for it, though, would take several seconds and some finger-counting.
* In ''Anime/LupinIIIDeadOrAlive'', Olèander is able to see through Lupin's disguise because [[spoiler: of how it felt to kiss Pannish]]. In the Dub, Lupin jokes he needs more practice. In the Sub, [[spoiler: it is because Pannish never smoked]]. She doesn't seem upset about the disguise, and continues to work with him afterwards.
* ''Manga/{{Naruto}}'': Team 7 tries their utmost to avoid this when they have to meet Sasori's spy whilst disguised as Sasori. It actually works; the spy doesn't realize he's dealing with an imposter... [[spoiler:he was just intending to double-cross Sasori anyway.]]

* In the early 1990s ''Franchise/SpiderMan'' arc where Peter Parker's parents returned from the dead, May realized they were imposters when they refer to the wrong date for their anniversary, indicating that they somehow didn't know about their secret wedding several months prior.
* Happens twice in ''ComicBook/PaperinikNewAdventures'':
** When a group of Evronians ([[EvilCannotComprehendGood who just don't get the point of many expressions of emotions and tend to ignore them]]) disguise themselves as Xerbians to trick [[PhysicalGoddess Xadhoom]] into wearing a restraining device they have no idea of what a Xarghon is. A Xarghon is a traditional Xerbian welcome dance that any child on their homeworld would have known about, leading to Xadhoom (who really loves dancing to boot) to see through the ruse... [[{{Troll}} And amuse herself with their attempts at guessing what a Xarghon is]] before she blows them up.
** When Paperinik infiltrates [[{{Ruritania}} Belgravia]] disguised as Grigorji Grimka, son of the president, to try and find out who in the government betrayed and tried to kidnap him, he was not informed that Grigorji had [[BrawnHilda a large and irascible fiancee]] who is allergic to flowers and he doesn't like, thus allowing her to see through his disguise when he's nice and offers her flowers (thankfully she wasn't the traitor and limited herself to see who the impostor was and why he was there, [[BigDamnHeroes leading a group of loyalists to the rescue at the right moment]]). This is caused by Grigorji, who is an idiot, purposefully leaving this detail out alongside the fact he ''keeps two lions as pets'' while [[NiceJobBreakingItHero telling his lover, who is actually one of the traitors, that he's still in America and the Grigorji coming home is an imposter]].
* Played for laughs in a ''ComicStrip/FoxTrot'' strip; Paige tries to forge her fathers signature on an excuse note to get out of gym class, but her teacher catches on because the I's are dotted with little hearts.
* In a ''Comicbook/{{Supergirl}}'' Annual, the titular heroine tries to pass herself off as Comicbook/LanaLang's niece when a cop questions her. She realizes too late she doesn't even know what her alleged job is.
* ''ComicStrip/KnightsOfTheDinnerTable'': Brian's character gets into trouble attempting to enter a walled city during a ''Grunge Warrior'' game when he presents the guards with forged papers that identify him as an ambassador from a country that ceased to exist 30 years previously.

[[folder:Films -- Animated]]
* The title character of ''Disney/{{Mulan}}'' does this when asked her name. Her family name (which she must use as part of the cover story) is Fa, but she hasn't thought of a ''personal'' name, leading to a very awkward conversation where Mushu tries to secretly help her come up with a name. One of his suggestions is [[PunnyName Ah Chu]], which would have lead to the cover identity being ''Fa Ah Chu''.
* In ''Disney/WreckItRalph'', Ralph tries to pose as a candy cane tree inspector while quizzed by Vanellope, but she sees through this lie immediately because he clearly knows nothing about her game world.
* In ''Disney/TheJungleBook'', Baloo disguises himself as an ape to have a ball at King Louie's party. However, Louie then smacks him on the back, causing his coverings to fall off.

[[folder:Films -- Live-Action]]
* Played with in the movie ''Film/SuperBad'', where Fogell gets a terrible fake ID that only has the name "[=McLovin=]". (The fact that there's no first name is bad enough, but the signature on the license clearly says ''[=McLoving=]''.) It actually appears to fool the cops, and they end up going on an adventure with the kid. Subverted in the end, when they reveal that they immediately saw through the fake but wanted to have some fun and show him that not all cops are assholes.
* In ''Film/RomyAndMichelesHighSchoolReunion'' they are pretending to be "successful businesswomen" to impress people. It is only when a waitress asks them what business they are in that they realise they may have neglected a vital element of their cover story. During a dream sequence, Michele actually supports her cover by rattling off a complex but plausible method of developing the adhesive for Post-It Notes, which they claim to have invented. Interestingly enough, it wasn't scripted - the actress improvised thanks to actually having an education in science.
* In ''Franchise/StarWars'': ''Film/ANewHope'', Han and Luke are disguised as stormtroopers aboard the Death Star, to rescue Princess Leia, when they're forced into a shootout with some real stormtroopers. After killing them, Han rushes to a com unit to try and fool the troopers on the other line that nothing's wrong, and the following conversation takes place:
-->'''Han:''' ''[sounding official]'' Uh, everything's under control. Situation normal. \\
'''Voice:''' What happened? \\
'''Han:''' Uh, we had a slight weapons malfunction, but uh... everything's perfectly all right now. We're fine. We're all fine here now, thank you. How are you? \\
'''Voice:''' We're sending a squad up. \\
'''Han:''' Uh, uh... negative, negative. [[BlatantLies We had a reactor leak here now]]. Give us a few minutes to lock it down. Large leak, very dangerous. \\
'''Voice''': Who is this? What's your operating number? \\
'''Han''': Uh... \\
(''Han shoots the intercom'') \\
'''Han''': (''muttering'') Boring conversation, anyway... (''shouting'') LUKE, WE'RE GONNA HAVE COMPANY!
* In the final sequence of ''Film/{{Stalag 17}}'', Sefton confronts [[spoiler:Price]], the [[TheMole Nazi double agent]] in the [=PoW=] barracks. [[spoiler:Price]] stands up pretty well to questioning, until Sefton asks him when Pearl Harbor was bombed. He knows the right day and time, but [[spoiler:forgets about the time difference. He gives the time in Germany, when it was about six hours earlier in the US.]]
* In ''Film/AceVenturaPetDetective'', Lois Einhorn is revealed to be Ray Finkle when she yells in a man's voice at commentary of the "Kick Heard Round The World" that drove him over the edge.
* In ''Film/ToBeOrNotToBe'', the German spy gives himself away by not knowing who Maria Tura is, despite her being a hugely famous actress in his supposed hometown.
* In ''Film/{{No Man of Her Own|1950}}'', Helen tries to convince her doctors that she isn’t Patricia Harkness, but they think she's just confused because of the train crash she survived. The Harkness family then takes her in (never knowing what Patricia looked like). She decides to go along with it because she’s penniless and has a newborn baby in tow, but she makes a lot a simple mistakes about the Harkness' son (Hugh) who Patricia was married to.

* ''Literature/SkulduggeryPleasant''. Scapegrace has a problem that causes him to invent a twin brother, of course he gets every detail right and thinks of everything.... except one of the names.
* ''Literature/HarryPotter''
** In ''Literature/HarryPotterAndTheChamberOfSecrets'', Harry & Ron use Polyjuice Potion to pretend to be Crabbe & Goyle, but their infiltration of Slytherin House is stymied by the fact that they don't know how to get in to Slytherin's chambers. They ask a passing student, but she's from Ravenclaw. Fortunately, Crabbe and Goyle are so dim that they're not really acting out of character. They asked the Ravenclaw where the common room was, and were lead there by Draco. They had an OhCrap moment when Draco asked them the password, but were saved when Draco remembered it before they did. Other instances of them being out of character for Crabbe and Goyle are when Harry didn't know what Azkaban was and when both of them forgot to laugh at a ''Daily Prophet'' article where Ron's dad gets in trouble with the Ministry.\\\
In the movie, Harry almost gives it away by still wearing his glasses. He quickly excuses them as reading glasses, causing Malfoy to stare at him skeptically and, [[ThrowItIn courtesy of an adlib by Tom Felton]], to remark that he didn't know "Goyle" knew how to read.
** [[ChekhovsGun The specific example of the location of the Slytherin common room comes up again]] in ''Literature/HarryPotterAndTheDeathlyHallows'', when Scabior says people have claimed to be Slytherins when caught by his gang of Snatchers but couldn't say where the common room is. Because of his previous experience, Harry can actually answer this question which throws Scabior for a moment, but not enough to let Harry go.
* ''Literature/XWingSeries'': Face Loran, in disguise as [[SmallNameBigEgo Captain Darillian]], stumbles into one of these when Admiral Trigit uses an Imperial Intelligence code phrase which he doesn't recognize but Darillian should know instinctively. The Alliance agents do come up with the explanation of the code phrase for him (after a few seconds), but Trigit is still suspicious. [[MagnificentBastard Naturally]], Face bluffs his way out of it, first by [[SarcasticConfession seemingly confessing the truth]] ([[ThatManIsDead "I'm not the Zurel Darillian you knew"]]), then by distracting Trigit with [[RefugeInAudacity a tale of having been in love with Ysanne Isard]].
** Or, more specifically, of having an unrequited crush on Ysanne Isard, bringing out a TON of background info to overwhelm Trigit, AND finally bringing up a detail only someone who met Ysanne Isard would know. Namely, the specific perfume she wears, which Face knew because he met her once, and only once. The ship applauds.
* ''Literature/ASongOfIceAndFire''. While on her quest to find the fugitive Sansa Stark, [[ActionGirl Brienne]] of Tarth claims she's looking for her sister, but forgets to think up a false name for her. It's a moot point anyway, as most people can tell who she's looking for just from the description, given that she's rather high-profile (when [[spoiler:the heir to the North]] is a suspect in [[spoiler:the murder of the King]], word gets around) and there's [[BountyHunter a lot of other people searching for her]].
* ''On Wings of Eagles'' by Ken Follett. 'Bull' Simons insists that the EDS men he's taking out of Iran learn the details on their fake passports off by heart. Everyone thinks this is an unnecessary precaution until just before they reach the border, when they're stopped at a guerilla checkpoint and grilled on these exact details.
* Several of these in ''The Spycatcher's Omnibus'' by Lt. Colonel Oreste Pinto. In one case, Pinto is alarmed to discover a high-ranking British official who is a notorious ladies man has got himself a new SexySecretary, a refugee from German-occupied France who did not pass through the routine security clearance. He has to do an ad-hoc interrogation there and then, with the official constantly demanding Pinto hurry up (despite the fact that such interrogations normally take days). Pinto suddenly has the idea of telling the woman to take off her shoes, which reveals her nice soft feet -- despite her claiming to have walked all the way from France over the mountains to Spain. The official is flabbergasted when Pinto informs him his secretary has just confessed to being a German agent.
* The Literature/TommyAndTuppence novel ''N or M?''
** Tuppence is undercover as an "unofficial" agent at a seaside inn attempting to root out a German spy. She has made up her own elaborate back story where she has three sons, one serving in each branch of the military, who send her letters in secret code. At one point, she talks about her "own two", momentarily confusing her real-life twins with the made-up sons. When called on it by the inn's owner, she covers it by explaining that two of her sons were very close in age and spent more time together than with the third sibling.
** Tommy, undercover at the same time, averts this; his background was made up by the intelligence agency he's working for to fit in neatly with his existing life and not be too elaborate to remember.
* ''Literature/TheExecutioner''. Inverted in "Brothers in Blood", where a woman tells Bolan about a group of 'hunters' (actually a hit squad hunting Bolan) "dressed up in denims and huntin' caps and hikin' boots and so forth -- nothing wrong with them, and ''that'' was what was wrong. They looked like they'd stepped out of an [[http://global.llbean.com/ L.L.Bean catalog]], outfitted up and ready to go. I say to myself, Miss Jane, here is a mess of folks trying to look like something they ain't."
* ''Literature/NickVelvet'': In "The Theft of Nick Velvet", the killer accidentally exposes himself while claiming to be an artist from Johannesburg and talking about the excellent southern light in his studio. As Nick points out, in the southern hemisphere, artist's want northern light.
* ''Flashman and the Great Game''. Literature/{{Flashman}} is posing as a recruit for a native cavalry unit in India. Despite claiming that he has no previous military experience, the OldSoldier quickly spots him as a fraud because Flashman is unconsciously standing the correct distance from his desk, and has bridled his pony in the regulation manner. Fortunately this serves as an InfractionDistraction as everyone assumes he's just on the run from a tribal blood feud, rather than a British officer in disguise.

* The British comedy series ''Series/{{Spaced}}'' features Tim and Daisy, who are pretending to be a couple in order to rent an apartment. Though they attempt to be as thorough as possible by learning a multitude of mundane details about each other ("I forgot what you got for your fifth birthday!" "Miniature drum kit"), they get caught in their lie while fumbling around regarding what day they had sex first vs. what day they kissed first.
** A much worse mistake is barely averted as, just before they go in, they realize they've never learned each other's names.
* Subverted in the ''Series/{{Farscape}}'' episode "Losing Time." The crew are informed that an "energy rider" had invaded the body of one of them and that they can find out who it is since the rider won't know "details of the heart" like family members. They get misdirected when a new member of the crew tells a different story about her background than the one she initially told them and they assume she's lying. In truth she'd been lying the first time.
* ''Series/StarTrekTheNextGeneration'': In 'Future Imperfect', a boy posing as Riker's son misses a vital piece of information about the woman he claims is his mother - [[spoiler: she only ever existed as a hologram]].
* ''Series/BurnNotice'':
** Came up as early as the second episode. Mike is impersonating a friend of a friend of the Villain of the Week, Quentin King. Quentin slips a BluffTheImpostor into an offhand remark about their mutual cellmate Paco. The Department of Corrections file Mike used as a source for his cover ID didn't say whether Paco drank, so Mike guesses that he didn't. He was right[[note]]He points out later that he had a 50/50 chance of being right, and correctly guessed that it was a BluffTheImpostor question. He then points out in the narration that this happens to spies ''all the time''[[/note]].
** In later episodes, he gives examples of what to do if the Cover Identity Anomaly slips during a BluffTheImpostor moment: ''keep lying''[[labelnote:*]]"Some spies, when their cover looks like it's going to be blown, will drop the pretense and retreat. ''Good'' spies will ''lie harder''."[[/labelnote]]. In a similar case to the above, he's asked a question and gives the wrong answer (it's another drinking question, and he says that the friend of a friend never drank). When the target calls him on it, Mike simply says that the friend of a friend gave up drinking in prison and found religion, which the target thinks about and accepts.
* ''Series/GameOfThrones''. Brienne is escorting Jaime Lannister back to King's Landing when three Northern soldiers recognise him as the notorious Kingslayer. Naturally they deny it, with Brienne claiming Jaime is a thief she is taking to Riverrun to be thrown in the dungeons.
-->'''Soldier:''' I've a question for you both, and I want you [[StereoFibbing both to answer it at the same time]]. I count to three, you both answer. What's his name? One...two...three...
-->''(Brienne and Jaime exchange a MeaningfulLook, then she kills all three soldiers.)''
* This almost gets Callen killed in an episode of ''Series/NCISLosAngeles''. The team intercepts the communications of a terrorist cell and realize that the terrorists are expecting a new member to arrive whom they have apparently never met before. They arrest the terrorist and Callen takes his place. However, the cell's leader actually went to school with the man Callen is impersonating. They were very young at the time and never became friends so Callen is able to bluff his way through the questions he is asked. However, he trips himself up because in their hurry to make the switch, the team failed to realize that the new terrorist is left-handed. The cell leader clearly remembered this about his former schoolmate and when he sees Callen write using his right hand, he knows that they are being tricked.
* In the ''Series/BeingHumanUK'' episode "The War Child", Eve is being smuggled into a [[PuttingOnTheReich concentration camp]] by a freedom fighter claiming to be her father. Unfortunately, Mr. Snow tests this story by asking the man what colour Eve's eyes are. He doesn't know.
* ''Series/{{Graceland}}'':
** Narrowly averted in the pilot. Mike has to go undercover as the brother-in-law of a low level drug dealer in order to prevent Russian mobsters from killing the dealer's family. The brother-in-law is a real person with a criminal record that the Russians are aware of. Mike only vaguely matches the man's description and is shorter and thinner than him. They compensate by having him wear platform shoes and blaming the weight loss on drug use. Mike still almost gets caught when he has to tell the Russians about a murder he claims to have committed and the FBI agents listening in on the conversation from MissionControl have to quickly create a fake crime report that matches what Mike said and insert it into the relevant police databases.
** In another episode Mike pre-empts this when he pretends to be a Marine selling stolen military weapons. Almost immediately after selling the weapons to a gang, the gang gets hijacked by another gang which takes those weapons. When the angry gang leader suspects a setup and questions Mike about his whereabouts during this hijack, Mike angrily tells them that he was on base and they can easily verify it by checking with his duty sergeant. The sergeant does not exist but Mike knows that, unlike the Russian mobsters, these gang bangers do not have the contacts to verify his story or even confirm that someone with that name is even enlisted in the Marine Corps.
* In the pilot episode of ''Series/{{Cheers}}'', Sam isn't fooled by a teenager's fake ID, because it not only claims he's over forty, it's a falsified military ID.
* ''Series/PersonOfInterest''
** An executive at a computer security company tries to send flowers to the parents of an employee killed in a traffic accident. When it turns out that the parents do not exist, she quickly realizes that the man was a Chinese spy. She also realizes that someone high up in the company must have been working with the spy or this would have come up on a routine background check. It turns out that [[spoiler: many of the company's employees, including most of the executives, were Chinese spies]].
** The Machine has Root and Shaw infiltrate a CIA black site by having them pretend that Shaw is a CIA agent delivering Root as a prisoner. The Machine is unable to obtain all the correct security codes so Shaw has to say that she was in a hurry and forgot to get the new codes. The suspicious guard is about to radio in to his superiors for verification of her identity but his radio malfunctions. Shaw is able to tell him the correct procedure for resetting the radio. The procedure was designed specifically to prevent unauthorized personnel from using the black site's equipment so the guard accepts this as proof that Shaw really is part of the unit.
** Reese is captured along with three other BadassInANiceSuit mercenaries in "Prisoner's Dilemma". All have impeccable cover identities, but [[InspectorJavert FBI agent Donnelly]] is convinced one is the [[PersonWithTheClothing Man in the Suit]] vigilante, so it becomes a race to maintain Reese's cover until one of the mercenary's cracks.
** In Season 4, Reese has a cover identity as a police detective. While working as a tactical instructor, a female trainee notes that he uses military tactics despite his file not showing the appropriate background. Reese fudges the issue by claiming he was taught by an instructor who was a Gulf War veteran.
* One episode of ''Series/DegrassiJuniorHigh'' has Snake trying to get alcohol for a party. It would all be well and good except for the fact that the fake ID doesn't even have a picture on it.
* ''Series/DeathInParadise'': In "Death of a Detective", a woman has assumed the identity of her sister. However, she had never read the novel on which her sister did her dissertation at Cambridge.
* On ''Series/{{Turn}}'' an American agent is trying to infiltrate British-occupied New York by posing as British officer who was captured by the Americans and is being exchanged in a prisoner swap. The agent is quickly discovered when he does not know his regiment's motto and later makes a few more mistakes including failing basic European dinner etiquette by holding his fork in his left hand.
* An episode of ''Series/VeronicaMars'' deals with Veronica's dad, who has been temporarily reinstated as sheriff, cracking down on bars that serve alcohol to minors despite the obviously fake [=IDs=]. The only two teens whose [=IDs=] are ''very'' good Sheriff Mars happens to know personally, and he also happens to know that they were laminated using his own ID card printer. He then has his deputies conduct random ID checks at bars. When that doesn't yield results, he sets up the same two teens with obvious fakes (with pictures of [[Music/BonJovi Jon Bon Jovi]] and [[Music/TheNotoriousBIG Biggie Smalls]]) and has them drinking non-alcoholic beer at a bar about to be inspected by one of his deputies. When the deputy doesn't attempt to arrest the two teens despite the obvious fakes, the sheriff has him and three others fired.
* ''Series/TheSaint'': In "The Organisation Man", Templar, working undercover for British military intelligence, has infiltrated a small [[PrivateMilitaryContractor private army]] whose current assignment is to [[spoiler:liberate a captured, high-profile spy]]. They're disguised in the stolen tartans of a detachment of Scottish soldiers who were due to take over guard duty, and on handover, are being inspected by the current guard commander. Their disguises are perfect (as befits a regiment known for their punctilious attention to detail), up until [[OhCrap the point]] when the commander notices that [[spoiler: they've all placed their [[NationalWeapon sgian-dubh]] knives in the wrong sock - the right rather than the left]].


* [[MysteryWriterDetective Paul Temple]] and his wife Steve, in addition to revealing impostors by using [[BluffTheImpostor a question or comment]], have a couple of occasions where an impostor simply gets one detail wrong.
** In ''Paul Temple and the Alex Affair'', Temple gets a phone call from his friend Leo Brent, whom he has sent to stake out a hotel. The caller is a plausible impostor, but his error is [[spoiler:addressing Temple several times as 'Paul', when, as Temple remarks to Steve, Brent ''always'' calls him 'Temple'.]]
** In one episode, Steve receives a phone call from another very plausible impostor claiming to be her husband. The only way she knows it isn't him is [[spoiler:because he uses the expression "By George!" rather than his usual "By Timothy!"]]

* This is a suggested possibility for ''TabletopGame/{{Shadowrun}}'' characters whose false identities fail security scans. On a critical glitch, a suggestion is that some part of the data is clearly false (e.g. an elf's SIN identifies him as a female troll).
* This entire trope is a game mechanic in ''TabletopGame/DemonTheDescent''. Long story short: The PlayerCharacters are the titular demons and can create [[DealWithTheDevil pacts]] with motals, which trades some part of the mortals life (fiancee, house, university education etc) for money, power, love, any of the usual stuff really. The reason Demons do this is so they can integrate whatever the mortal traded away onto their own supernatural disguises to make them more "real", but the catch is only things directly involved in the deal get changed. So the Demon might gain the true love and affection of someones fiancee, but all of their family will remember them being engaged to a completely different person, or you might gain a diploma with all the paperwork to match, but none of the university lecturer's or anyone in the graduating year will remember them. When these discrepancies start getting noticed they start to wear away at the Demon's disguise, which leaves them vulnerable to being noticed by [[TabletopGame/VampireTheRequiem other]] [[TabletopGame/MageTheAwakening supernatural]] [[TabletopGame/WerewolfTheForsaken creatures]], or worse, the [[BigBad God Machine]].

* One mission in ''VideoGame/MechAssault'' has the player pilot a captured enemy Thor into a Word of Blake base to download some intel from their computers. The disguise almost works, until one of the Blake officers asks you to transmit your ID code or be fired upon. Fortunately, they wait just long enough for Foster to download the intel.
* In ''VisualNovel/PhoenixWrightAceAttorneyTrialsAndTribulations'', an impersonator doesn't know that the person he's imitating recently suffered an injury that made him [[spoiler: unable to hear out of his left ear]]. When a witness who was fooled by the imitation testifies that the person was [[spoiler: wearing an earpiece in his left ear]], Phoenix has to point out that it makes no sense.
* In ''Videogame/TalesOfSymphoniaDawnOfTheNewWorld'': [[spoiler: Emil Castagnier]]. [[spoiler: Being the summon spirit Ratatosk in human form, Emil]] lacks a lot of information that would be expected from a resident of [[spoiler:Palmacosta - fishing, the Desian Human Ranch nearby, etc.]] Subverted in that [[spoiler: he is unaware of what he is BeneathTheMask for most of the game]]
* In a mission in ''VideoGame/Hitman2SilentAssassin'', Agent 47 can adopt a disguise of a "Lord Sinclair" to get close to his target (a female doctor). If she asks 47 for the name of "his" wife, though, he won't know what to say before eventually randomly coming up with "Elsie" (which is way off the mark), blowing his cover.
** Subverted in the 2016 ''Videogame/{{Hitman|2016}}'', where in the Bangkok level 47 can disguise himself as a drummer of his target's band. If he's asked to show off his skills, 47 plays a decent beat and his disguise remains intact.
* In ''VideoGame/SaintsRowTheThird'', the Boss disguises himself as Cyrus Temple, the leader of S.T.A.G., to infiltrate their base and save Shaundi. While MagicPlasticSurgery means the looks and voice are perfect, the Boss makes little to no attempt to try and ''speak'' like Cyrus. Depending on your chosen voice and gender, this can result in "Cyrus" doing things like hitting on his subordinate, talking about how cute a guy is, or speaking in various accents.
* [[spoiler: Renard Vulpes]] in ''VideoGame/AviaryAttorney'' goes by Juan Querido, prince of Spain. Problem is that's actually pretty easy to check - there are no significant princes of Spain and "Querido" is probably not a real name. However, only his defense attorneys bother to look that up. Despite him being charged for murder and attempted murder of the king of France.

* In ''Webcomic/TheLeagueOfSuperRedundantHeroes'', an alien named Zoolkor [[MeaningfulName Lizard-Face]] [[CardCarryingVillain Human]][[NamesToRunAwayFromReallyFast killer]] has what seems to be the perfect disguise for infiltrating human society, but the ''name'' she uses as such, [[http://superredundant.com/?comic=302-undercover well, needs work.]]
* In ''Webcomic/SurvivorFanCharacters'', Bonnie returns in one season disguised as "Sarah", a seemingly sweet therapist for "Bonnie" who's actually an actress hired to impersonate her. She invents a sob story as Sarah about a dead mother, which comes back to bite her in the rear end when she's unable to tell Brandi the name of her supposed dead mother.

* This has happened many times to WesternAnimation/BugsBunny, usually with his ears or tail sticking out from his disguise.
** This has also happened, most likely as a ShoutOut to the above, in the ''WesternAnimation/TinyToonAdventures'' episode "The Looney Beginning" when Montana Max sees Buster and Babs' tails poking out of their outfits.
* ''WesternAnimation/TheSimpsons'':
** The page-quote above in "Blood Feud", where Homer attempts to pretend he's Mr. Burns... except he doesn't know what Mr. Burns's first name is.[[note]]His full name is Charles Montgomery Burns, and he generally goes by his middle name when asked.[[/note]]
** In the "Treehouse of Horror X" story "Life's A Glitch, Then You Die", when Homer pretended to be the pianist from the movie ''Film/{{Shine}}''. When asked for his name, he responds "[[IAmNotShazam Shiny McShine]]".
** In "Lard Of The Dance", when attempting to steal Springfield Elementary's grease, Homer and Bart are confronted by Groundskeeper Willy. When Willy demands to know what is going on, Homer claims to be a foreign exchange student from Scotland. When Willy presses him for where in Scotland, Homer hesitantly states "North... Kiltown?" When Willy says that [[IAmOneOfThoseToo he's from North Kilttown]] and asks if he knows Angus [=McLeod=], [[RefugeInAudacity Homer inverts the situation, stating there is no Angus [=McLeod=] in North Kiltown and it is]] ''[[RefugeInAudacity Willy]]'' [[RefugeInAudacity falsifying his identity]].
* ''WesternAnimation/AvatarTheLastAirbender'' has Sokka trying to pass himself and his sister Katara off as Aang's parents when he gets in trouble with his teacher at a Fire Nation school[[note]] Trust us, ItMakesSenseInContext, it really does[[/note]], leading to the hilariously badass PaperThinDisguise identify of Fire. ''[[InherentlyFunnyWords WANG]]'' [[AwesomeMcCoolName Fire!]]. And his wife, Sapphire Fire. As with many examples of RefugeInAudacity on the show, this works beyond any reasonable expectation [[RuleOfFunny because it's funny.]]
* In the ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' episode "Spike At Your Service" the main characters stage a fake Timberwolf attack for Spike to rescue Applejack from, and Spike is fooled at first, until he notices that the fake Timberwolf doesn't have bad breath.

* This is the point of "Security Questions" on websites when you need to reset your password; they're intended to foil someone pretending to be you, by asking questions that only you should know the answer to.
** Some places invert this and actually advise you to put something that is completely wrong (but that nobody would guess) as the answer, for example if the question is "What is your birthday?" put "Puppy", so that if the pretender does find out your info they can't get into your accounts. (This assumes, of course, that the system will accept such an answer to ''that'' particular question; for a system that accepts only ''dates'' for a "birthday" question, one can still enter a wrong date.)
* Standard tradecraft for spies when communicating is, to give a hint to their controllers if someone was faking their communications, to have a subtle challenge code that, assuming the spy hadn't gone full DoubleAgent, would be something the faker wouldn't be able to respond correctly to or even realize they were expected to respond to. The same principle was used for dead-drops: often a legitimate drop required some subtle thing at ''another'' location to verify the drop.
* One quick check used in stores to challenge customers who appear too young for the purchase (typically alcohol and/or cigarettes) and might have a fake ID is to ask what year they were born. Someone faking their age is likely to trip up and give their actual birth year or obviously have to stop and think about what year they would have had to have been born to be legal.
** A similar practice works (less reliably) for signature forgers. While the person is signing their name, if they're asked a question that they have to stop and think about, they're more likely to mess up their signature if they're not used to writing it.
* Meanwhile, on ''Website/NotAlwaysRight'', a youngster trying to buy cigarettes is [[https://notalwaysright.com/pleased-to-fake-your-acquaintance/74562/ using her older sister's ID]], so she looks like the photo and knows all the facts... but [[spoiler: the shop clerk went to high school with said sister]].