->''I see you supized I speak Engrish so werr!''
-->-- '''Dave Barry'''

When a character who has been speaking perfect, unaccented English (for whatever region he's in), gets revealed to be a spy or covert operative from some other country, from that point on, he instantly reverts to a thick accent from his native language. A character revealed as a robot will suddenly switch to a classic "robot" speech pattern.

This is distinct from OohMeAccentsSlipping in that it is not a poor acting display by the performer, but instead a deliberate (and inexplicable, unless the character is aware his cover is blown) thing written into the story. Bear in mind that in works using a TranslationConvention, the transition from fluent English to, say, Russian-accented English may represent a genuine transition from English to Russian.

From a linguistic standpoint, it can actually make sense, as maintaining an accent or dialect perfectly is exceptionally difficult until you get extremely familiar with it. Most people would cease to exert the effort if they knew they didn't have to. Makes less sense for a DeepCoverAgent, however -- once you get to the point that you can speak the language at near-native level, then it's harder to revert ''back''.
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!!Examples:

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[[folder:Anime & Manga]]
* Nanami from ''LightNovel/SakurasouNoPetNaKanojo'' was from Osaka, and would relapse into KansaiRegionalAccent whenever she is angry or flustered.
* Kobato from ''LightNovel/BokuWaTomodachiGaSukunai'' tries to act like her favorite anime character -- down to speaking in a haughty tone -- but will snap back into her natural Kyushu accent whenever she gets flustered.
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[[folder:Comic Books]]
* Wolfsbane from the ''NewMutants'' initially had a Scottish brogue, which she lost during the second volume of the series. She inexplicably began using her accent again in ''Comicbook/{{X-Factor}}'', which was eventually explained in an issue of ''New X-Men''. Turns out she tried to hide her accent from her friends in order to seem "cool," but no longer felt any pressure to do so once she joined X-Factor.
* In ''ComicBook/ThePunisherMAX'' arc "Kitchen Irish", the story revolves around a group of criminals who all have a connection to a recently deceased [[TheIrishMob Irish Mob]] boss who has sent them each a piece of a map that will show where he hid the riches he amassed over his life. The associate of one of them, Michael Morrison, slips into his natural Irish accent when his boss Finn Cooley surprises him after having taped on his multilated face after losing a mask designed to keep it on. Michael asks if it'll slip, and Finn snarks "You mean like your accent?" Much later, after multiple clashes with each other and The Punisher, the criminals all gather in a bar to put together their pieces of the map. After they see where the treasure is, they all get ready to kill each other. Michael smashes his drink on the bar counter, and in a heavily accented speech tells them that they don't need to keep killing each other, and they don't need to bring the horror of UsefulNotes/TheTroubles to the States. They all put their guns away.
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[[folder:Fan Work]]
* In the ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' series ''Fanfic/RainbowDoubleDashsLunaverse'', Trixie will slip back into her Neigh Orleans accent when drunk.
* In the {{Anime/Pokemon}} fanfic, ''FanFic/TheTrainerFromAFarAwayLand'', Ash/Satoshi is mostly fluent in Isshu, but his native Kanto accent shows when he tries to pronounce N's name.
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[[folder:Film]]
* ''SpiesLikeUs'': Once the [[spoiler:mission contacts]] are revealed to be Russian spies, in the subsequent interrogation scene, they have thick Russian accents.
* ''Film/TheRocketeer'': The Nazi spy, [[spoiler:Neville Sinclair, played by TimothyDalton]], after speaking perfect English the whole movie, ZUDDENLY HAZ ZE GERMAN ACCZENT VUNCE HE ISS EXPOZED, JA!
* Norm in ''Film/TheresSomethingAboutMary'': he even forgets himself and nearly uses his real accent in front of the woman he was trying to fool, before trying to recover but giving up and telling the truth. Justified, in that he was putting on an upper class English accent and is actually American.
* Done by Ann-Margaret in NeilSimon's ''The Cheap Detective'', when detective Peter Falk tricks her into revealing that she's Russian -- she is unable to pronounce the word "baubles".
* ''Film/{{Watchmen}}'' Adrian Veidt/Ozymandias speaks with an American accent for formal situations, but with a German accent in private. The actor who plays him invented a backstory for the character in which his father was a Nazi, causing him to conceal his German ancestry in shame.
* Was supposed to happen with Dr. Scott in ''TheRockyHorrorPictureShow'', but for some mystifying (to O'Brien and the audience alike) reason Jonathan Adams had an accent even before being called von Scott.
* Done in ''Film/SpyHard'', after Dick Steele (agent WD-40) makes love to a woman, she is revealed to be a spy for General Rancor with a heavy Russian accent. Apparently, she doesn't slip into her native accent even in the throes of passion but drops it immediately before trying to shoot Steele. He doesn't notice it, though.
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[[folder:Literature]]
* This is inverted in ''Literature/TheMoteInGodsEye''. One character (the Chief Engineer, no less) usually speaks with an exaggerated Scottish accent, and like all inhabitants of 'New Caledonia' places great emphasis on his proud Scottish heritage, despite this being the far future when there isn't much left of the old cultural distinctions. Another character remarks that he loses the accent when he gets excited, which he loudly declares a lie--without using the accent.
* In ''Literature/TheLiesOfLockeLamora'', Locke drops his false [[FantasyCounterpartCulture Vadran]] accent the few times he's completely found out.
* In rare moments of overwhelming emotion--usually fear or rage or both--Felix in ''Literature/DoctrineOfLabyrinths'' will lose his posh accent and slip into a Lower City one. Ultimately he will always begin using his fake accent again the moment he notices.
* In ''Literature/ToKillAMockingbird,'' the Finch family's black housekeeper, Calpurnia, normally speaks with a "standard" accent but suddenly starts using black vernacular when she takes the kids to her all-black church. She later explains that it would seem rude to speak "properly" in front of other blacks since most of them aren't as educated as she is.
* In ''[[Literature/TakeshiKovacs Altered Carbon]]'', Reileen Kawahara spends most of the story speaking in a very formal, cultured accent in order to project an air of respectability. When she's under great stress and her facade cracks, however, she reverts to speaking in a vulgar Fission City accent.
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[[folder:Live Action TV]]
* ''{{Poirot}}'' did this once with a supposed socialite who reverted from RP to a Cockney accent after being exposed.
** Possibly a ShoutOut, the same thing happens in "The Unicorn and the Wasp", the Creator/AgathaChristie homage episode of ''Series/DoctorWho''.
* On ''{{CSI NY}}'', a man pretending to be Jewish is revealed to be a German former Hitler Youth soldier. Even after 64 years of pretending to be a non-practicing Polish Jew, marrying a Jewish woman, and raising an Orthodox Jewish son, he reverts to his German accent when his crime is revealed.
* Happens to a German spy who had tried to infiltrate ''Series/HogansHeroes''.
* Spoofed in ''Series/GetSmart''. Max asks why TheMole is suddenly speaking in a fake German accent after being unmasked. He replies, "Vot accent? Zis is my veal voice!"
* Inverted on an episode of ''Series/{{Bones}}'': the intern with the thick Middle Eastern accent slips into his actual American accent. It turns out that he was faking the accent to avoid having to explain to the practically StrawAtheist Brennan and Squints why he took his religion so seriously: if he was an immigrant, it would make sense for him to clutch at his roots, but he apparently felt that the members of Brennan's team wouldn't be able to understand why a rational, scientific mind like theirs could not only be religious, but ''devoutly'' so.
** Bonus points for Bones actually noticing that he got the accent ''wrong''. He was supposed to be Iranian but his fake accent was Jordanian. Bones knows these things but didn't think it important enough to ask.
* More of a Personality Relapse, but before being revealed to the audience as a Terminator in ''TheSarahConnorChronicles'', Cameron talks and acts like a perfectly natural teenage girl. Afterwards, even in situations when she's with people who don't know she's a Terminator, she seemingly loses this ability to act natural and instead stares at people oddly and is generally robot-y in her speech patterns and reactions.
* Averted in ''{{Blackadder}} Goes Forth'', where a British spy who has been spying on Germany returns and ''retains'' his extremely heavy German accent, causing others to assume he was a German spy.
* Averted in the classic ''Series/{{Star Trek|The Original Series}}'' episode "The Trouble With Tribbles" -- when [[SilkStalkings "Arne Darvin"]] is found out to be a Klingon spy, his demeanor remains pretty much the same humanish demeanor that it was. (When he returns for ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'', he does go just a bit hyper when he's transferred from Cardassian custody.)
** Even that is explained away by finally getting a caffeine fix (the closest Cardassians have to coffee is a fish juice).
* At least a couple of examples from ''Series/TwentyFour''.
** In season 1, the Serbian man impersonating Ted Cofell spoke flawless English with a neutral American accent. However, after his cover was thoroughly blown and Jack Bauer began to interrogate him, he cursed Jack in Serbian and spoke in a thick Serbian accent.
** In season 8, the assassin Davros, in his cover identity of an NYPD officer, speaks in a New York accent when trying to get a coworker to switch shifts with him, but once it becomes clear that the guy won't budge, Davros pulls out a gun and switches to a Russian accent.
* In an episode of ''{{Chuck}}'', the titular character encounters a British handler (played by TimothyDalton) who turns out to be the criminal mastermind Alexei Volkoff. When he reveals himself, he suddenly switches to a very bad Russian accent. In the subsequent episodes, though, he speaks with a perfect British accent, even in his Moscow headquarters. Later explained when he turns out to have been British all along, just brainwashed to think he was Russian.
* AmericanAccents version, in ''Series/{{Warehouse13}}'' Sally Stukowski dropped her Texan accent when Mrs. Frederic informed her they knew she was from Connecticut.
* On ''Series/JustShootMe'', a couple pretending to be Nina's birth parents drop their facade in the elevator and start speaking French as they discuss the next phase of their plan.
* Grand Maester Pycelle in ''Series/GameOfThrones'', who is a master at ObfuscatingStupidity, spends most of his time in public pretending to be a doddering old man, complete with a weak, quavering voice. In the S2 Finale, however, when he is alone with Tyrion he drops the act entirely, conversing in his natural, strong voice.
* Averted on ''{{Series/Highlander}}'', where Duncan only uses his Scottish accent in flashbacks. His modern one is ambiguous, deliberately so.
* In the ''Series/DoctorWho'' episode "Love and Monsters", the alien speaks English with a rather affected and unconvincing posh Southern accent when disguised as a human, but when he's unmasked as an alien, his accent shoots way OopNorth (the actor's natural accent).
** Also, in "Tooth and Claw", the Tenth Doctor puts on a Scottish accent while trying to pass as a native of the Scottish highlands. Later, whilst being chased by the monster of the episode, he forgets to keep using the accent and is caught by Queen Victoria, helping her resolve in rejecting the Doctor's world. Notable in that DavidTennant, the actor playing the Tenth Doctor, is actually Scottish, although the accent he uses in the episode isn't his regular accent.
* Mild example in ''Series/BreakingBad'': most of the time, the Chilean Gustavo Fring speaks in perfect American English of the sort most Americans consider "unaccented." When he allows his Chilean accent to creep into his speech, it's a sign that he's showing what's BeneathTheMask. This can be a rare sign of trust and affection, or it can be a sign that [[OhCrap it's time to start running]].
* Averted in ''Series/{{MASH}}'' in the episode 'Dear Comrade' when Kwang, a spy for the Korean People's Army, masks his perfect fluency in English with broken Korean Engrish.
** Over the course of the episode, he becomes fond of a couple of the personnel on the base, and before going back to his division he decides to have a drink with them. Heavily inebriated, he declares that "When all is said and done, you're not such bad fellows!" and B. J. points out that the drunker Kwang gets, the better his English becomes. Kwang hesitates before replying that 'it must be the whiskey', and pours himself another drink.
* Occurs in RealLife in ''ThePeoplesCourt'': when Cuban-born Judge Milian gets especially upset, her Spanish accent becomes more noticeable.
* The criminal of the week in ''Series/{{Elementary}}'' is encountered by a detective in a hospital and speaks perfect American English. After the cops finally figure out that she's a French national, she suddenly slips into her "natural" accent (the actress is American).
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[[folder:Other]]
* In the TabletopGame/{{Clue}} VCR game from the 80s, Miss Peach reveals herself to be M. Brunette's daughter and therefore French. She subsequently delivers most of her remaining dialogue with a French accent (as opposed to the Southern drawl she'd used until then).
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[[folder:Radio]]
* Half-way through the ''AudioPlay/BigFinishDoctorWho'' drama "Invaders from Mars", the character Glory Bee suddenly reveals that she is vorking for Matherr Rasha, ant hencefarth eess eencapable off maintaining her prreeviasly parrfect Amarricn aksant.
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[[folder:Theater]]
* In ''Theatre/SweeneyToddTheDemonBarberOfFleetStreet'', when Sweeney Todd is visited at his shop by Adolfo Pirelli, the SnakeOilSalesman that he showed up in an earlier scene, Pirelli reverts to an Irish accent, revealing his actual non-professional name to be Daniel Higgins.
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[[folder:Video Games]]
* In ''VideoGame/FreedomFighters'', once [[spoiler:your advisor with suspiciously accurate information]] is revealed to be a Russian general, he is calling out to you through a sewer. Your character does not recognize his voice until he uses his disguise American voice once more.
* In ''VideoGame/BioShock1'', [[spoiler:Fontaine speaks with an Irish accent as Atlas, and with an American accent as himself.]]
* ''Franchise/AceAttorney'': Though not a spy, Maximilian Galactica speaks in a very CampStraight manner, until things start to get a little to stressful. Then he breaks down and starts weeping and talking with a heavy southern accent. Presumably this happens with culturally-appropriate accents in Japan, as in both versions Max is a country bumpkin who made good.
* When The Spy in ''VideoGame/TeamFortress2'' is disguised, his voice clips change to match that of whoever he's disguised as. Which is more a gameplay mechanic, but fits the trope because he reverts to his normal accent once he drops the disguise.
* ''VideoGame/FinalFantasyXIII'': When Vanille first shows up, she slips in and out of an Australian accent to the point where it sounds like it's a bad case of OohMeAccentsSlipping, but after [[spoiler:you find out she's from Pulse]], she gets the accent full-time, matching Fang's.
* In ''VideoGame/StarWarsTheOldRepublic'', the Imperial Agent normally speaks with a thick British accent common to the rest of the Empire, but when s/he goes undercover he drops the accent completely. If his/her cover is blown at any part of the story s/he drops the accent once s/he's positive they know s/he's a spy and not just bluffing him/her.
* In ''{{VideoGame/Borderlands 2}}'', in Moxxxi's bar, if you tip her, she will occasionally relate a story of how she used to be part of the Hodunk clan and why she left it. She then starts to slip into a more redneck-like accent similar to the other Hodunks in the game, then quickly corrects herself, and asks you not to tell anyone about it.
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[[folder:Western Animation]]
* When the King of the Renaissance Faire is deposed and hit with a sexual harassment lawsuit on ''KingOfTheHill'', he immediately reverts from YeOldeButcheredeEnglishe to a thick Texas accent.
** Even funnier when you realize the voice actor in question was Creator/AlanRickman.
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