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->''"The park was deserted except for a member of [=MI9=] trying to recruit someone who, to their later mutual embarrassment, would turn out to be also a member of [=MI9=]."''
-->-- ''Literature/GoodOmens''

Somebody [[AWolfInSheepsClothing disguises themselves]] as a member of some group [[TheInfiltration to sneak among them]]. However, it turns out everyone else in the area is also in disguise. Primarily used in comedy.

A favorite scene is to have the primary detectives bust an operation, only to find out that the people they're busting are cops themselves. Depending on how much hilarity the writers are going for, there may be as many as three or four squads in the room at the time.

Once the multiple operations are revealed, JurisdictionFriction tends to ensue, with the squads arguing about who takes point, who can stick around, and who has to leave.

If they turn out to have been on the same side too, then it is RightHandVersusLeftHand. Sometimes the result of a GambitPileup. May be part of revealing TheOnlyBeliever. Might also drive a character to demand: "Okay, will the real [X] please stand up?" - and then ''everybody'' stands up.

Compare/contrast IAmSpartacus and ResistanceAsPlanned.

'''Due to the nature of this trope, spoilers abound.'''



[[folder:Anime & Manga]]
* ''LightNovel/{{Slayers}}'':
** In an episode of ''Slayers Next'', the team infiltrates a kingdom dedicated to training priestesses, and takes it so seriously it's supposedly a LadyLand which will execute any man found near its borders, never mind in the city. As it turns out, it's actually full of {{Wholesome Crossdresser}}s -- even the ''princess'' is actually the ''prince'', forced to pretend to be a girl because his crazy mother didn't want to annul the rule, yet didn't want to execute her son either.
** In another episode in ''Slayers Revolution'', every employee and guest on the cruise ship they take turns out to have been hired by their enemies to get the [[LaserBlade Sword of Light]].
* In one of the ''Anime/ProjectAKo'' [=OVAs=], every single customer at the Lepton-mothership-turned-restaurant turns out to be a disguised spy... all for different organizations. Cue BlastOut.
* One episode of the ''Anime/{{Patlabor}}'' TV show has them helping the Japanese intelligence service pick up a Soviet defector and his experimental HumongousMecha in a seaside resort town. Every single person there is said to be a spy of some sort. The one that really takes the biscuit being:
-->"You see that dog crossing the road there? It's a Mossad spy dog!"
* This is kinda what happens in ''[[LightNovel/HaruhiSuzumiya The Melancholy of Haruhi Suzumiya]]'', except that Kyon, the MetaGuy [[TheProtagonist protagonist]], isn't one of the "wolves" and is dragged into the title character's Club For Finding Aliens, Time-Travelers, and Espers by force. However, it soon turns out that every other member of the club (including the founder) is some kind of supernatural being that they are supposed to look for. In a way, the title character ''[[InvokedTrope invoked]]'' this trope without being aware of it, due to being a WrongGenreSavvy RealityWarper.
* The second series of ''Anime/CodeGeass'' introduces the Britannian Office of Secret Intelligence, whose entire function is to spy on Lelouch. By the middle of the series, practically the entire organisation has either been blackmailed or mind-controlled by Lelouch into working for him.
* In the ''Manga/SoulEater'' manga, we already knew Crona was acting as a spy for Medusa when the DWMA started getting suspicious. It turned out there were ''four'' spies working for three different people (Crona for Medusa, Justin for Asura, and the two women at the cabaret Spirit visits for Arachnophobia) as well as a student that was really a witch (though she wasn't a spy).
* In ''Manga/TsubasaReservoirChronicle'', it turns out that only ''one'' human member of the original party isn't a spy -- Kurogane. And two of the spies [[ManchurianAgent aren't even aware of it]].
* In ''Anime/TheIrregularAtMagicHighSchool: The Girl Who Calls The Stars'', everyone wants basically the same thing: to prevent another world war. However, because of the national and factional tensions left by the ''last'' war (and the wrench that [[PoweredByAForsakenChild the Watatsumi slaves]]' existence throws into everyone's plans) it is about halfway into the movie before any of them realize this. Fortunately, all the soldiers involved know a common language and a [[EveryoneWentToSchoolTogether surprisingly high degree of them attended school together]].

[[folder:Comic Books]]
* This happens in one of the prequel comics for ''Film/SmokinAces''.
* One strip of ''ComicStrip/TwistedToyfareTheatre'' had Reed Richards turn into a Skrull and gloat to Susan Richards about having tricked her into having sex with him. She promptly turns into another (male) Skrull and replies "Bob, you idiot."
* Creator/MarvelComics' ''ComicBook/SecretInvasion'' got close to this trope at times. For example, one meeting of Marvel's Illuminati (the big movers and shakers of Earth's superheroes) ended when everyone at the table realized he was a Skrull. They hadn't even known themselves!
* The City in ''ComicBook/{{Miracleman}}'' was created as a place to dump all the spies whose lifetime of paranoia had left them mentally unprepared to live in a {{Utopia}}. Everyone who lives there is a spy, but they all think ''most'' of the others are the ordinary civilians they're protecting.
* One ''ComicBook/{{Nightwing}}'' comic featured an entire town where almost every inhabitant was someone in the Witness Relocation program.
* A sub-series of Italian stories in the ComicBook/MickeyMouseComicUniverse has Goofy writing stories in various genres, with himself as protagonist and Mickey Mouse as his sidekick. The stories mostly make fun of various genres and their tropes. One of "his" stories from 2003 has the duo as undercover cops posing as prisoners, their mission being to befriend a certain prisoner and learn his secrets. They soon find out that their superiors went a bit overboard with their planning. With the exception of the secretive prisoner, the prison population consists entirely of undercover cops.
* In the Creator/ECComics Science-Fiction [=SuspenStory=] "Infiltration," a secret U.S. government agency for ferreting out Martian invaders who use hypnotic screens to disguise themselves as human beings discovers that it has been infiltrated by an alien. It turns out the agency is actually controlled by Martians, who are all too glad to rid themselves of the Earth "alien" in their midst.
* In one of Alan Moore's ''ComicBook/ThargsFutureShocks'' stories, a werewolf is loose on a spaceship and plans to feast on all the unsuspecting humans within. Naturally, every person on the vessel turns out to be a werewolf, to their consternation. It's implied that Earth came up with this as a means of getting rid of all the supernatural beings in their midst; the passengers shown boarding another ship at the end are all plainly vampires in PaperThinDisguise.
* By the final issue of ''ComicBook/TheSuperiorFoesOfSpiderMan'', [[spoiler:the entire gang except Shocker is discovered to be a double agent working for some other gang or supervillain.]]
* In ''ComicBook/TheInvisibles'', all four members of the Metropolitan Police's secret [[TheMenInBlack occult crime squad]] Division X were actually Invisible infiltrators. Only one of them knew this from the start, and at least one of the others [[MemoryGambit wasn't even aware]] that he himself was an infiltrator.
* In ''ComicBook/{{Iznogoud}}'', the Caliph's rival/occasional friend Sultan Pulmankar turns out to have sent two spies to collect informations in his palace. As it turns out, one of the spies disguised as the titular Great Vizar's right-hand man Wa'at Alahf, with the intent to spending time with Iznogoud and get informations out of him... while the other spies dsiguised as Iznogoud himself, with the intent to do exactly the same thing with Wa'at Alahf. Predictably, they end up meeting each other instead of the real Iznogoud and Wa'at Alahf, who were minding their own business. By the time they figure out the mistake, they had been trying in vain to con informations out of each others for ''weeks''.

[[folder:Comic Strips]]
* ''ComicStrip/TheFarSide'':
** The TropeNamer, even if it doesn't use those words in the caption, is a comic where a wolf in a crude sheep costume he designed in order to infiltrate a flock of sheep finds out that it's composed entirely of other wolves in sheep costumes.
** In another one, a guy is standing in a crowd of people, yelling "the vampires are everywhere!" Meanwhile, across the street there's a pair of workers hauling a large mirror, and the man screaming about vampires [[ProperlyParanoid is the only person with a reflection]].
* A Creator/GahanWilson cartoon in ''Magazine/{{Playboy}}'' shows Hispanic-looking revolutionaries overrunning the dictator's office. The dictator, confronting the revolutionary leader, snarls, "You fool -- I'm CIA, too!"
* ''Magazine/{{MAD}}'':
** In a Don Martin gag strip, all the passengers on an airplane look around shiftily. Then they all get up at the same time, brandishing a weapon, and shout "All right, nobody move! This is a hijack!" Everyone looks at each other and sits down, embarrassed.
** In another, a woman gets her purse snatched and yells "Stop thief!". Everybody in the immediate area (including a little boy and a dog) freeze and raise their hands.

[[folder:Fan Works]]
* In the ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' fanfiction ''[[http://www.fimfiction.net/story/48341/changelings-changelings-everywhere Changelings, Changelings Everywhere]]'' the mane cast discovers that Rainbow Dash was a changeling all along, then that Pinkie Pie was another changeling sent to find her... the escalation doesn't really stop until it's revealed that Celestia is literally the only pony who isn't secretly a changeling. Several ponies who were replaced with changelings turned out to be changelings in the first place. The story ends with two of the changelings [[ScrewThisImOutOfHere going to get lunch]] while everyone sorts out who's on what side.
-->"Is anyone here actually a pony? Are ponies even a real thing?"
* In ''[[https://www.fimfiction.net/story/122849/changeling Changeling,]]'' which has a similar premise to the above (everyone but Celestia, Luna, Twilight Sparkle, Trixie, and [[spoiler:Prince Blueblood]] are changelings), the trope is namedropped by Celestia.
-->'''Celestia:''' There are at least five thousand separate changeling hives trying to take over Equestria, and none of them know of more than one or two other hives. It's like a flock of wolves, all trying desperately to pretend that they're sheep.
:: She also finds it rather amusing that neither Cadence nor Shining Armor knows the other is a changeling.
* In the ''Franchise/HarryPotter'' fanfiction ''FanFic/MakeAWish'', all of the Death Eaters on watch when the Death Eater lair was blown up were spies; fortunately, all of them chose that moment to report to their respective organizations, so none of them were killed.
* In ''Fanfic/HarryPotterAndTheMethodsOfRationality'', Professor Quirrell decides to allow spies between the armies for the battles he sets up. It gets so out of hand, that the only answer to the question in the page quote has to be "no." The character who gives Hermione this intelligence turns out to be a ''quintuple'' agent. There are ''three'' armies. [[spoiler:The other two are Dumbledore and a disguised Quirrel, both of whom achieved their objectives far better than any of the official sides.]]
* In ''Fanfic/DiamondAndSilversExcellentAdventure'', Diamond Tiara and Silver Spoon accidentally time travel to the past, and wind up among LaResistance in the ancient earth pony kingdom. At the next meeting, the majority of the Resistance reveal themselves to also be disguised time travelers.
* ''FanFic/AhAintGotNoAckcent'': After spending much of the story convincing Applejack to use a "Manehattan" accent instead of her regular "[[SouthernBelle Southern]]" one in order to appear more "cultured", [[spoiler:much to Rarity's JawDrop-inducing surprise, ''she'' is the only pony at the exhibit that ''doesn't'' has a Southern accent and is trying to hide it for appearances' sake.]]
* In the ''Franchise/HarryPotter'' fanfic ''[[https://www.fanfiction.net/s/12756784/1/A-Flock-of-Wolves Flock of Wolves]]'', a rather boring meeting of Death Eaters is interrupted by Dolohov (and Bellatrix, and Augustus, and Macnair, etc) revealing that he's a spy. About the only members who aren't undercover are Avery and Lucius- although ''he'' only joined the group to hobnob with rich people. Fortunately, all these conversations take place while Voldemort is off somewhere else.
* In the ''Literature/WarriorCats'' fanfic ''[[https://www.fanfiction.net/s/12888612/1/A-Different-Outcome A Different Outcome]]'', it turns out that half the cats in [=ThunderClan=] have broken the warrior code at some point- and they all realize this on the same night.

[[folder:Films -- Live-Action]]
* ''Film/TheBeliever'': Danny starts a class advocating Nazism, and is later told most "students" are police informants, not actual neo-Nazis.
* In ''Film/CaptainAmericaTheWinterSoldier'' it's revealed that [[spoiler:HYDRA rebuilt itself and infiltrated S.H.I.E.L.D. ''from the beginning.'' While loyal S.H.I.E.L.D. agents are implied to outnumber HYDRA operatives, there are still way too many for them to count as just TheMole.]]
* In ''Film/TheDeparted'', the only two named members of TheIrishMob who aren't undercover cops or confidential informants are Mr. French and Fitzy.
* ''Film/{{Freaked}}'' has Ricky [[MuggedForDisguise jack a milkman for his uniform]] to try and escape Freek Land, only to run into the rest of the freaks who also had the exact same idea. While they argue, the BigBad notices the dozen freaks dressed as milkmen from his window and [[UnusuallyUninterestingSight simply remarks that it must be a very competitive route]].
* Early in ''Film/MontyPythonsLifeOfBrian'', Brian's mother disguises herself as a man to attend a stoning. Every other 'man' there was also a woman wearing a beard. ([[RecursiveCrossdressing Even the ones who are played by men.]])
* ''Film/MyBlueHeaven'', a mafioso turned protected witness is accused of a crime by the local police. In order to avoid being convicted, he offers the police a deal: he knows of some mafia in the area who are looking to buy stolen goods. He gives them the information, they drop the charges. The police burst in, only to find the buyers are actually undercover FBI agents doing a stakeout.
* In ''Film/OSS117CairoNestOfSpies'', the hero (who is a French spy passing for a businessman) meets the other foreign businessmen: all but one are also spies.
* ''Film/ToLiveAndDieInLA''. An informant tells the CowboyCop of a courier arriving in town with money for a drug buy. As his superiors won't approve the sting money he needs to entice the BigBad, he and his partner decide to rob the courier, only to find themselves shot at (the courier is accidentally killed by a stray bullet) and chased by an ever-increasing number of well-armed men with vehicles and radio communication. The two cops barely escape, only to be briefed next day about an FBI sting operation that went wrong and resulted in the death of an undercover agent.
* In the movie ''Film/{{Traitor}}'', DeepCoverAgent Samir is tasked to place thirty suicide bombers on buses as part of a terror attack. He puts them all on the ''same'' bus...

* In the ''Discworld/MonstrousRegiment'', the main character [[SweetPollyOliver disguises herself as a man to join the army,]] only to find that nearly every single member of her squad is also a woman in disguise. [[spoiler:Even the ''very'' masculine [[BoisterousBruiser Sergeant Jack Jackrum]].]] In fact, the only male is the decidedly effeminate Lt. Blouse. Their disguises, including that of the ''pregnant'' Shufti, are so effective that when they opt to try the old "pretend to be the washerwomen" trick, Blouse deems himself the only one sufficiently capable of acting female to pass muster. (And he's ''right'' -- he makes past the guards just fine, while the rest of them have rather more difficulty. The real washerwomen, who are mostly the indentured wives of the soldiers on their side, aren't fooled by Blouse's antics, but play along anyway.)
** And when the girls are put on trial for impersonating men by the StrawMisogynist army, Jackrum sends about half of the officers out of the room, and reveals to the other half he knows they're all women. Roughly a third of the army's high command turns out to be female.
** Even better is when Jackum does this, he sees the way the women are looking at each other and is stunned to realize how ''every single one of them'' thought ''she'' was the only one in the army doing this.
** Also, one of Literature/{{Discworld}}'s [[FootnoteFever many, many footnotes]] relates how aliens have had to stop abducting people from the Earth, because so many different extraterrestrial species have been doing so, or monitoring each others' attempts to do so, that they've only succeeded in abducting other aliens, and they want to sort things out to determine if there even ''are'' any earthlings. They begin to suspect there is exactly [[BigfootSasquatchAndYeti one native with large feet]].
** ''The Discworld Companion'' describes how the [[LaResistance Turtle Movement]] in [[Discworld/SmallGods Omnia]] protects itself from the CorruptChurch by only meeting in small cells, in which everyone wears masks. Which is why the senior churchmen who are members don't know that every other senior churchman is a member as well.
* ''Literature/TheManWhoWasThursday'' by Creator/GKChesterton is about a police officer who infiltrates a group of anarchists only to discover that all of the anarchists are also policemen. The President of the anarchists turns out to be the officer who recruited all of them. [[GainaxEnding He may or may not also be God.]]
* ''Let's Go to Golgotha'' by Garry Kilworth is about time travel tourism where one of the most popular trips is Christians travelling back in time to witness the Crucifixion. The tourists are disguised as Jewish citizens. In the end, the protagonist suddenly realizes that the crowd condemning Jesus to the cross is composed entirely of tourists from the future, and that no actual Jewish Jerusalemites of 33 A.D. are present at all.
* Creator/PhilipKDick wrote a story called ''The Eyes Have It'' where an InspectorJavert character who hunts aliens (indistinguishable from humans except for glow-in-the-dark eyes) and dissects them informs his superiors that there is an [[TheMole alien spy]] among them. It turns out they are all aliens except him.
* Creator/PhilipKDick's ''The Game-Players of Titan'', which involves aliens from Titan that can make themselves appear human, has a scene in which the protagonist discovers that he is the only member of the anti-alien resistance cell he's joined who isn't an alien sleeper agent.
* Creator/HarryHarrison's ''Literature/BillTheGalacticHero'' had Bill getting recruited by an insurgency and then by military intelligence; eventually a bust occurs and every insurgent turns out to be (or at least says they're) working for the military.
* ''Literature/TheStarDiaries'':
** One of Creator/StanislawLem's Ijon Tichy stories has a planet full of agents disguised as robots trying to infiltrate an evil computer's (nonexistent) robotic army.
** In another of his stories, during hearings on the robot infiltration problem, every member of the hearing turns out to be a robot.
* ''Literature/GoodOmens'' as seen in the the page quote.
* ''Beach Music'':
** The novel contains a dark take or two on this. In one case, Capers, a member of the main character's TrueCompanions, joins an anti-UsefulNotes/VietnamWar student group with Shyla (another member of the nakama, and becoming her lover along the way) only to betray both the anti-war group and the nakama by having been an undercover agent the whole time. He tries to minimize the damage by saying that Shyla and the others were just innocent dupes, and the leader of the group was the real trouble. Turns out the group leader was also an agent.
** Another case is something of an inversion. An undercover police officer tries to turn a peaceful student rally into a riot, but is caught and kicked out immediately because they realize he's much too zealous and dressed like too much of a stereotype to possibly be real.
* In the'' Literature/TimeWars'' novel ''The Pimpernel Plot'' there's a scene where, apart from Literature/TheScarletPimpernel and his nemesis, everybody in the room turns out to be an undercover time traveller, with about half of them working for the villain and the other half there as backup for the heroes. ([[MythologyGag Possibly a bonus in-joke for readers familiar with the source novel]]: in the original version of the scene, apart from the Pimpernel and his nemesis, the room is empty.)
* Friedrich Dürrenmatt's comedy/tragedy/drama ''The Physicists'' takes place in an asylum for {{Mad Scientist}}s. As it turns out, however, none of the three eponymous physicists is actually insane: one of them is ObfuscatingInsanity to prevent worldly authorities from exploiting his scientific breakthrough, and the other two are undercover agents from CIA and GRU planted there to convince him to cooperate with their respective governments. And ''then'' it turns out that the female head of department of the asylum is the only one who ''really is'' insane.
* Creator/TimDorsey does this twice with his ''Florida Roadkill'' books. The first time, undercover agents of three different law enforcement agencies infiltrate a drug ring and try to bust each other (leading them to wonder if all drug dealers in Florida are secretly undercover cops). The second time, a group of people planning to overthrow Castro is composed almost entirely of agents of Cuban intelligence. The only exception is a retired CIA officer. The sad thing is that they all know it and yet they still make plots they have no intention of implementing and send reports back to Cuba about what was discussed in the meetings.
* In Creator/HarryHarrison and Ant Skalandis's novel ''Literature/{{Deathworld}} vs. Filibusters'', the Pyrrans have finally managed to defeat the pirates only to find out that Henry Morgan, pirates' leader, and several of his {{Number Two}}s were working for various agencies all this time, all under deep cover in order to expose the entire organization. The Pyrrans don't care and execute Morgan for all he has done (being an agent doesn't excuse murdering and pillaging).
* In ''Literature/MotherNight'', one soviet spy is called a failure for "building an espionage apparatus entirely out of CIA infiltrators." But the joke's on the CIA: he never cared about spycraft, and just used the KGB's money to fund his art, which is entirely apolitical.
* A variation in ''Literature/TheDresdenFiles'' book ''Literature/DeathMasks'', where Harry appears on a talk-show talking about the supernatural. The guests are himself (a wizard), an "ectomancer" (psychic who can communicate with the dead), a Roman Catholic priest from the Vatican talking about faith v. the supernatural, and a university professor who specializes in debunking claims of the supernatural. Harry only agreed to the show so that he could speak to the ectomancer, as the man would not otherwise meet with him for fear of being caught in the crossfire in the ongoing supernatural war. Harry soon discovers that the other two guests ''also'' appeared on the show in order to have inconspicuous meetings with him on business that is completely unrelated to the other people there. [[spoiler:Not only did they want to talk with him, but they were each also a different type of supernatural being. It is ultimately revealed that every single person on the "Is the supernatural real?" panel had a power or was a supernatural creature of some kind.]]
* In the Literature/RepairmanJack series, the [[ChurchOfHappyology Dormentalist]] higher echelons consist entirely of people who are desperately hiding the fact that they're "Nulls", meaning that they've failed to develop the psychic powers promised to devout Dormentalists. Naturally, the leader of the cult introduced the concept of "Nulls" specifically because he knew they never would gain such powers, as the faith's core creed is a load of garbage.
* By the end of the Claire Malloy mystery novel ''Mummy Dearest'', it's turned out that practically everyone Claire's met on her trip to Egypt is either a spy, an informant for spies, or a member of the smuggling ring that the spies have been hunting for. And every one of the spies works for a different Egyptian, British, American or international investigative agency.
* In ''Literature/MurderOnTheOrientExpress'' by Creator/AgathaChristie, Poirot has to determine which of the twelve train passengers performed a revenge killing in the night. The solution is that they all did it.

[[folder:Live-Action TV]]
* In a really funny season opener of the short-lived show ''Series/TheAgency'', there was a bust of suspected terrorists, and it turned out it was [[http://www.youtube.com/watch?v=g39xIewgGaM all undercover cops]] from different agencies.
* In ''Series/AgentsOfSHIELD'', it slowly becomes clear that every single member of TheTeam on [[CoolPlane the Bus]] except for Coulson is spying on ''someone'', whether it be Coulson, each other, or just S.H.I.E.L.D. in general.
** Skye is a mole for [[spoiler:the Rising Tide, a hacktivist organization similar to Anonymous. Coulson wins her over relatively quickly though, convincing her that if S.H.I.E.L.D. is Big Brother, it's [[BenevolentConspiracy a protective and well-meaning one]] that just goes overboard sometimes.]]
** May is a mole for [[spoiler:Director Fury, of all people, sent to keep an eye on Coulson and make sure [[CameBackWrong nothing went wrong with his resurrection.]] She also built the team (by providing Fury with a list of roles which he translated into a mission order to give to Coulson) so that she could take Coulson down and repair him if it became necessary.]]
** Ward is a mole for [[spoiler:HYDRA and its Centipede program, searching for the secrets of Coulson's resurrection. He seduced May in order to cement his cover -- unaware that [[{{Irony}} she had all the information he needed]].]]
** [=FitzSimmons=] are a mole for [[spoiler:no one, at least at first. Mostly they just had the bad luck to end up in the middle of a bunch of conspiracies. They do start working against Coulson when he won't let them properly study the drug that brought him back to life, though. They want to hook it up to a S.H.I.E.L.D. mainframe to figure out how to mass-produce it and save countless lives, while he is freaked out about where it came from and possible side effects.]]
** And then of course we have [[spoiler:Coulson himself. He was in charge of the T.A.H.I.T.I. project that was working on the drug to bring back an Avenger in case they fell in battle, and recommended it be shut down since there were horrific side effects and the only thing that ''barely'' worked was erasing all memory of the treatment from the subjects' minds. He became its first success, but a few days after he discovered this, he began to exhibit those psychological side effects himself.]]
** In the following season, Agents [[spoiler:Morse and Mackenzie are spies for a splinter faction of S.H.I.E.L.D. that is seeking to supplant Coulson as Director. Agent Hartley was one for the same group as well, but she died before TheReveal.]]
%%* ''Series/{{CSI}}'' also did this with gun runners.
* ''Series/CSIMiami'' had a version that, [[AlwaysMurder as usual]], became murderous but didn't started that way. As the investigation on the murder of a cast member of a ''Series/JerseyShore'' {{Expy}} goes on, the Miami-Dade Police crew discovers that not a single one of the "party-frat" people on the cast were [[MeanCharacterNiceActor as debauched as they first looked]], going anywhere from geniuses to a priest-in-training that wanted to use his show cred once the run was over to try to attract people to church. The murderer turned out to be a HollywoodNerd M.I.T. graduate that wanted a social life and popularity ''that badly''.
* In an episode of ''Series/{{Cybill}}'', Cybill dressed up as a prostitute to research an acting role she'd accepted. She asked another lady of the night what it was like being a prostitute, but it turned out she was also an actress. They asked a third woman, but she turned out to be a journalist. The three asked a fourth woman, but 'she' turned out to be a male vice squad officer.
* In a ''Series/TheDailyShow'' episode spoofing {{Chatroulette}}'s recent media attention, Jon decides to try it out. Besides a couple of people showing their junk, everybody Jon encounters is either a reporter or another Daily Show correspondent. When he gets to Katie Couric, she even complains that she is trying to do a piece on Chatroulette but so far she only got reporters.
* ''Series/DoctorWho'': In "[[Recap/DoctorWhoS31E4TheTimeOfAngels The Time of Angels]]", the Doctor and River search for a [[NobodyHereButUsStatues Weeping Angel]] in a cavern that they think is full of ordinary statues. They're wrong -- the statues are ALL withered, near-dead Angels, and they're ''waking up''.
* One sketch in ''Series/DoNotAdjustYourSet'' has a very blatant policeman trying to infiltrate a criminal gang while they're planning a robbery. Eventually it turns that everyone there is a undercover agent of some sort. They decide to go along with the robbery anyway.
* In an episode of ''Series/{{Frasier}}'', the son of a wealthy woman is trying to prevent Frasier from hitting her up for a donation (to save his old school, which is on the verge of bankruptcy). Niles distracts the son by saying one of the caterers at the party is trying to get her to finance a play. When the son asks out loud if any of the caterers are trying to get a play financed, they surprisingly all raise their hands.
* There was an episode of ''Series/GetSmart'' where Max becomes a DoubleAgent to infiltrate a KAOS cell, but it turned out everyone in the cell was from another agency (FBI, CIA, Naval Intelligence, & Scotland Yard).
* The Original Flavour ''Series/LawAndOrder'' had a ([[AlwaysMurder lethal, naturally, considering this series]]) fallout from such an event during the 60s, where it turned out several supposed Communists/Hippie Protesters were actually cops and other agents spying on each other, and being purposely kept in the dark.
* ''Series/LawAndOrderSpecialVictimsUnit'' had the team attempt to infiltrate a pedophile "club" of sorts... only to discover that one of them was an FBI agent ''also'' setting up a sting. An exasperated Captain Cragen wonders aloud if this inability of the Good Guys to work together is why the Bad Guys keep staying ahead.
* One episode of ''Series/{{Louie}}'' was about Louie C.K. taking a part in a film as a cop, and ended with him going to a convenience store while still in costume as it is being robbed. He tries to trick them with his fake gun, but the prop is so cheap it wasn't even meant to be removed from the holster--doing so reveals it doesn't even have an upper half. The robber doesn't shoot him though because, as his partner is just now finding out, his gun is also fake.
* In the ''Series/MacGyver1985'' episode "Honest Abe", Mac gets shanghaied by his CIA agent friend Abe to take down a South American dictator and a corrupt Army Major (played by Ben Stein) supplying the former with weapons. Eventually, one of the Major's lackeys reveals to the other he's an FBI agent seeking to bring down the Major and promises him immunity if he cooperates... and the other lackey replies he doesn't have to since he's also an undercover agent for Office of Budget and Management. And via background checks they discover that Abe is a CIA agent (they thought he had retired) and Mac is with the Phoenix Foundation. Naturally they are dumbfounded at the revelation that they are involved in an operation involving ''four'' secret agents of different agencies while they previously thought they were acting alone.
* ''Series/TheMaryTylerMooreShow'' had an episode where Mary and Rhoda join a dating club for divorced people despite being single rather than divorced. At the end of the episode, it turned out that everyone there was single and not divorced except for the club founder.
* ''Series/{{NCIS}}'', too, when Tony and Ziva [[UndercoverAsLovers act as an assassin couple]]. Fortunately, Gibbs and Fornell quickly agree to work together. As the series progressed, they would continue to have JurisdictionFriction with pretty much every security-related branch of the government (the FBI, the CIA, the NSA, the ATF, the Department of Homeland Security...heck, even the local police aren't always cooperative!).
* On ''Series/NCISLosAngeles'', Sam Hanna infiltrates an MMA gym and is set up to fight an up-and-coming fighter named Jason Wyler--who turns out to be LAPD detective and future main character Marty Deeks.
* An ep of ''Series/NightCourt'' had the FBI run a sting on a visiting judge using Dan as a shill, attempting to get Dan to catch the judge on tape trying to bribe Dan; turned out a different group of FBI agents was running a sting on Dan using the judge, trying to get Dan to take a bribe. Both groups of agents burst in, and recognize each other...
--> "BERT?"\\
* Parodied on ''Series/{{The Office|US}}'', where ''every single'' member of a gun standoff turns out to be a double agent.
* More [[HilarityEnsues hilariously]], ''Series/Reno911'' did this with a drug sting. One of the protagonists suspected a store was secretly selling drugs, and tried to get the cashier to admit it without explicitly asking for drugs. The cashier was secretly an undercover cop, and was playing dumb to try to get the protagonist to explicitly ask for drugs.
* ''Series/SaturdayNightLive'' had a sketch called "Narc School" about a HighSchool where every single student was really an undercover narcotics agent.
* Humorously referenced on ''Series/StarTrekVoyager''. In the pilot episode Maquis rebel Chakotay finds out his First Officer Tuvok is a Starfleet undercover agent working for Captain Janeway. Later on in the season he finds out his girlfriend Seska is a spy for the Cardassians. In fact, she ''is'' a Cardassian.
-->'''Chakotay:''' You were working for her, Seska was working for them -- was anyone on that damn ship working for me?
* On ''Series/AngieTribeca'', Gelis goes undercover with some lifeguards to figure out who among them is part of a drug operation. The cops arrest the head of them only for him to reveal he's also LAPD. One by one, the other lifeguards start pulling out badges from FBI, ATF, Immigration, DEA and a few other agencies down to the IRS.
-->'''Angie''': Is not one person on this beach an actual drug-dealing lifeguard?!

* Music/TomLehrer introduced his song "The Wild West is Where I Want to Be" on the album ''Music/TomLehrerRevisited'' by saying, "A few years ago I worked for a while at the Los Alamos scientific laboratory in New Mexico. I had a job there as a spy. Now, I guess you know that the staff out there at that time was composed almost exclusively of spies... of one persuasion or another."
* One of the vignettes in Music/TheBonzoDogBand's "Rhinocratic Oaths" sees a disguised police sergeant carrying out a sting operation at a gay bar (homosexuality being illegal in Britain before 1966), only to find that all the other patrons are policemen... [[SubvertedTrope who beat him up]].

[[folder:Tabletop Games]]
* Occurs in ''TabletopGame/{{Paranoia}}''.
** ''Paranoia'' in general lives on this trope. The {{PC}}s are charged by The Computer to hunt down mutants and secret society members. Every PC is both a mutant and a secret society member.
** The Industrial Workers of the World (Wobblies), introduced in the supplement ''Acute Paranoia'' (1986). When Friend Computer [[GossipEvolution heard about]] this secret society, it sent Troubleshooters to infiltrate it and report back to Internal Security; however, since the RealLife Wobblies fell apart before Alpha Complex was created, [[ShootTheMessenger they were executed]] for [[FailureIsTheOnlyOption failing to find it]]. After several iterations, one clever team ''[[TakeAThirdOption created]]'' the Wobblies so they'd have something to "infiltrate". At first, ''every single member was an [=IntSec=] spy'', but later they started finding "real" members of the society... who were actually spies from ''other'' secret societies.
* In ''TabletopGame/EclipsePhase'' one of [[BenevolentConspiracy Firewall's]] favorite methods of dealing with suspected spies is to stick a bunch of them in the same lab or organization, and tell each of them that they suspect one of the others in the group of being a spy. Then sit back and watch the fireworks.

[[folder:Video Games]]
* In ''VideoGame/{{Prototype}}'', the game devolves into a three-way war between the [[ZombieApocalypse infected]], [[EvilArmy Blackwatch]], and the player character, [[HumanoidAbomination Alex Mercer]]. ''VideoGame/Prototype2'' seems to have the same setup (albeit with a new protagonist and Alex [[NotAsYouKnewThem now leading the infection]]), but as the game progresses, it's revealed that practically half of Blackwatch is secretly working for Mercer.
* In ''VideoGame/MetalGearSolid2SonsOfLiberty'', the confederacy of terrorists Raiden fights against has six key leaders: Solidus, Fortune, Ocelot, Olga, Vamp and Fatman. Of these characters three are secretly operating on behalf of the Patriots (Olga, Ocelot and Fatman) and one is secretly operating on behalf of Naomi Hunter (Vamp). Only Solidus and Fortune aren't answering orders from outside parties. However, Fortune was plotting to betray Solidus, who himself had anticipated her betrayal and was plotting to betray Dead Cell.
* [[http://cheezburger.com/7866688000 This comic]] about Wonder Trading in ''VideoGame/PokemonXAndY'' (a new feature in which you trade Pokémon with a random player without knowing what you're going to get).
* Get caught cheating in ''VideoGame/TitanFall'', and you will only be able to connect to servers reserved for cheaters.
* In ''Franchise/TheElderScrolls'' series' recurring [[FictionalDocument in-game book]] ''A Game at Dinner'', it is implied that nearly all of [[ManipulativeBastard Prince Helseth]]'s advisors are actually spies for some other group. Naturally, Helseth [[BatmanGambit gets one of the spies to out himself]] and [[CarryingTheAntidote accidentally poison himself]] in a fashion [[MasterPoisoner so gruesome]] that another spy in attendance, the writer of the document the book is based on, resigns on the spot.

[[folder:Visual Novels]]
* The basic premise of ''VisualNovel/VirtuesLastReward'' is that nine people are kidnapped and forced to play a DeadlyGame by someone called 'Zero'. As it turns out, [[spoiler:four of the players actively worked to create the game, and the other four know who Zero is, or can at least make an educated guess]]. The only two people who are as innocent as they claim are [[spoiler:an amnesiac and a young child, respectively]], given that [[spoiler:Alice probably knows everything Clover does]].
* The protagonists of ''VisualNovel/ZeroTimeDilemma'' are test subjects for a government experiment, and yet most of them are there illegitimately. [[spoiler:Akane, Sigma, and Phi are only there to conduct corporate espionage, Junpei threatened someone to get himself on the list, and Q is an A.I who was created specifically for the experiment.]]

[[folder:Web Comics]]
* Happens in the first ''Webcomic/SpyingWithLana'' storyline when [[http://spyingwithlana.com/comic/mx1/ the good guys kept getting meaningless assignments.]] ({{NSFW}}). The one in the story was actually a plot by the chief to fish out the double agent behind it.
* [[http://adventurers-comic.com/d/20011120.html One of Khrima's plans]] in ''Webcomic/{{ADVENTURERS}}!''
* In [[http://www.oglaf.com/kingshaped/1/ one strip]] of ''Webcomic/{{Oglaf}}'' (warning, most of the series is '''''very''''' {{NSFW}}), a king's aides reveal themselves as shapeshifting assassins, only for [[ThisWasHisTrueForm the king's death to reveal]] [[MoleInCharge he was another shapeshifter]].
-->'''Shapeshifter:''' Well, now I just feel like an idiot.
* ''Webcomic/DarthsAndDroids'' has an noncanon [[http://www.darthsanddroids.net/episodes/0411.html outtake strip]] in which Jim gets paranoid after encounters with shapeshifters and clones and says that [[TheyLookLikeUsNow anyone could be a shapeshifter clone]]. At which point the entire Senate confesses to being shapeshifting clones.
* ''Webcomic/{{Buttersafe}}:'' [[http://buttersafe.com/2013/06/27/wolf-in-sheeps-clothing/ Literal example.]] But then it gets recursive...
* ''Webcomic/ProjectFuture'' has several stories were various groups are shapeshifters in disguise without being aware of each other, including [[spoiler:Red Valentine]] and [[spoiler:Dark Lord Rising]].

[[folder:Web Original]]
* [[http://www.theonion.com/content/node/27823 This]] article from ''Website/TheOnion'' parodies the rumor that the Ku Klux Klan consists mostly of undercover policemen. Conversely, they also once made a reference to a child porn site being busted by authorities, and every single visitor to the site claimed to be a concerned citizen trying to infiltrate the site and bring it down from the inside.
** ''[[https://www.youtube.com/watch?v=DH6TBdN-lJc I, Despot]]'' is a one-man example, where an undercover journalist infiltrates a bloodthirsty reign of terror in {{Qurac}} ''as the dictator himself''.
-->''All told, I exterminated over 200000 of my own people, in a campaign of tyranny and murder. The mainstream media may have forgotten the terrors I forced my people to endure, but I'm still haunted by their screams... and by one disturbing question: If the world did nothing when I did this once, would it ''still'' say nothing if I did it again?''
* The premise of [[http://www.collegehumor.com/video/3602789/all-ra-floor this]] ''Website/CollegeHumor'' sketch is that at one time, Kwantlen University accidentally put all the Resident Advisers on one floor. HilarityEnsues as they gather around for a fun meeting not knowing that they're all Resident Advisers.
* Similarly, [[https://www.youtube.com/watch?v=1NPhg0d_lrk this Cracked]] sketch is that every member of a high school class is an undercover adult.
* The girl in [[https://notalwaysright.com/parlez-snooze-francais/33095/ this]] story from ''[[Website/NotAlwaysRight Not Always Learning]]'' deliberately says something rude in French to the class, to prove to her teacher that she's the only one in the class ''not'' using an online translator for her homework.
* In ''Podcast/WelcomeToNightVale'', it's revealed that everyone in [[spoiler:the entirety of Night Vale itself]] is a sleeper agent for the [[ExactlyWhatItSaysOnTheTin Vague Yet Menacing Government Agency]]. When they all get activated at the same time, they quickly decide to [[LetUsNeverSpeakOfThisAgain never mention it again]].
* The Wiki/SCPFoundation story [[http://www.scp-wiki.net/everyone-knows "Everyone Knows,"]] where it turns out that TheMasquerade no longer matters because ''every single individual in the entire world'' is involved with at least one organization dealing with the paranormal. Well, everyone but one person.
* A ''WebVideo/LoadingReadyRun'':
** A [[https://www.youtube.com/watch?v=IkurPdHe0VY Crapshot]] has a room full of undercover cops revealing they've all been pursuing the same criminal organisation for different crimes.
--->'''Cop:''' Is anyone here a real criminal?\\
'''Previously unseen cop:''' I'm not.
** [[https://www.youtube.com/watch?v=jvYx7QBYV10 Badly Broken]] does this with people who pretend to watch ''Series/BreakingBad'' to avoid feeling left out. As they commiserate with the guy who ended up hosting the finale because so many people were in the same boat and skipped it, they see ''Series/BetterCallSaul'' announced and decide [[WeAreNotGoingThroughThatAgain they'd better catch up.]]
--->'''Graham:''' [[LameExcuse Then Jerry dropped out because he suddenly converted to a religion that doesn't let you watch Breaking Bad.]]
* The senior leadership of the [[CardCarryingVillain New Pacific Order]] in ''Website/NationStates'' was, for most of its history, composed ''entirely'' of people who were sent to infiltrate it early on in its history and thought switching sides would be more fun than reporting back home to their original factions.

[[folder:Western Animation]]
* In an episode of ''WesternAnimation/TheAdventuresOfJimmyNeutronBoyGenius'', a picnic is accompanied by a series of parent-child games. Jimmy, who naturally despairs of [[BumblingDad Hugh]] winning anything unassisted, invents something that more or less instills hypercompetence in athletics. When [[TheRival Cindy]] wins after the device malfunctions, it's revealed that her "mother" is actually her bodybuilding aunt, which would mean the prize goes to the Neutrons - except that they fess up to cheating as well, at which point the presenter runs through every team present until near-terminally unathletic Carl and his father are revealed to be the only ones who haven't cheated in at least one of the events.
* PlayedForDrama in ''WesternAnimation/BatmanBeyond''. Terry attempts to stop an illegal weapons sale, but it turns out the 'dealers' were actually Gotham PD. When Batman intervenes, the buyers run for it and get away. Commissioner Barbara Gordon chews him out for his rash behaviour. "It took us two months to set up that sting, and two minutes for you to ruin it!"
* The ''WesternAnimation/DogCity'' episode "Disobedience School" had Bugsy Vile taking over the school and trying to turn the students into delinquents. After the climax, all students in his class turned out to be infiltrators from various police agencies.
* On ''WesternAnimation/{{Duckman}}'', a televangelist hosts a forum of other religious figures, who at the end are revealed to be fakes -- except for the Ayatollah, who just wants to improve his image in the states.
* ''WesternAnimation/{{Futurama}}'' featured an episode of robot soap opera ''All My Circuits'', wherein a "Previously On..." segment featured several clips of characters claiming they had amnesia. This culminated in a scene where Calculon sat all the characters down in a room and demanded, "Does anyone here ''not'' have amnesia?" No one can answer.
* On ''WesternAnimation/InvaderZim'', [[VillainProtagonist Zim]] and [[CloudCuckooLander GIR]] are once captured by even stupider aliens who thought they were an actual human and dog. These aliens' disguises are [[PaperThinDisguise even more pathetic]], such as human masks that they hold to their faces with sticks.
* A common gag in ''WesternAnimation/LooneyTunes'' versions of RedRidingHood; the wolf character dresses up as grandma to take her place in bed and wait for Red, only to find the bed ''already'' full of other wolves!
* In the ''WesternAnimation/MiraculousLadybug'' episode "The Evillustrator", a costumed superhero is tasked with protecting a girl who, unbeknownst to him, is also a costumed superhero.
* ''WesternAnimation/TheSimpsons'':
** In one episode Bart went to an auction to mess with the bids. When he won, he snickered and bolted for the door. At which point the auctioneer awarded it to the second highest bidder... who also snickered and bolted for the door. It is revealed that ''no one'' placed a serious bid for that item.
** Another episode had Lisa pretend to be part Native American. When she confesses her fraud during a Native American conference, almost everyone there reveals they were faking their ancestry as well, including one guy who was [[TotemPoleTrench two dwarfs in a raincoat for some reason]]. Ironically, Homer then mentioned that their family actually ''does'' have Native American ancestry.
* ''WesternAnimation/SpongeBobSquarePants'':
** Squidward and [=SpongeBob=] enter a dance contest together, with Squidward inside [=SpongeBob=] doing all the dancing. When they are found out and disqualified, all the other contestants reveal that they too had help. The prize went to the only one who danced on his own: Patrick, who was actually rolling on the floor because of a cramp.
** Similarly, Spongebob once tries to disguise as Mister Krabs when he molts his shell so he won't look like a sissy in front of his old buddies; once Mister Krabs makes his confession, the others all reveal that they, too, had something to hide (and Mr. Krabs points out that their embarrassing secrets are permanent, while his shell will grow back soon).
* ''WesternAnimation/TeenTitans'' has a PlayingWithATrope example. After finding not one but ''two'' undercover heroes, Brother Blood suspects this of the H.I.V.E Academy. "Was ''anyone'' in my school actually there to '''LEARN'''?" They were the only moles at the time but another student has a HeelFaceTurn later on.
* In the ''WesternAnimation/WanderOverYonder'' episode "The Bad Guy", Doomstone ''appears'' to be a WretchedHive, but all of its inhabitants are merely pretending to be cutthroats and badasses - because they assume everyone ''else'' is the genuine article.

[[folder:Real Life]]
* Famously, during the [=McCarthy=] era in the USA, the FBI had many of its members infiltrate the Communist Party USA. It was estimated that, at its peak, approximately ''two-thirds'' of the party were operatives on the FBI payroll.
* The Communist Party of Great Britain during the Cold War consisted of around a 35-35-30 split of Security Service agents, KGB agents, and genuine members...many of whom would either quit or join one of the other two groups.
* The Website/SomethingAwful presence on the conservative "alternative to facebook", The Tea Party Community. At this point it's not clear how many normal users of the site there even are anymore, mixed in with all the Something Awful trolls, trolls pretending to not be trolls, people trolling them intentionally... and trolls from other places, who don't necessarily realize it's been taken over by SA.
* Likewise the ratio of trolls to sincere members on [[https://en.wikipedia.org/wiki/Conservapedia Conservapedia,]] whose founder/lead editor Andrew Schlafly has gotten more and more paranoid about "liberal" (which he uses to mean anything short of the far right fringe) influence on his pet wiki... with the result that he consistently bans people who genuinely agree with most of his views as soon as they inevitably have a minor disagreement, and keeps the trolls who never disagree with him, ever (because they're only there to egg him on to [[https://en.wikipedia.org/wiki/Conservapedia#Conservative_Bible_Project new heights of ridiculousness and/or blasphemy]]). There is even a not so uncommon EpilepticTrees theory that Andy ''himself'' is a troll.
* The German extreme right-wing party NPD (Nationaldemokratische Partei Deutschlands, National-democratic Party of Germany) is infiltrated heavily by the Verfassungsschutz (Protectors of the Constitution, Germany's domestic intelligence agency). When talking about disbanding the party, the highest court ruled that with so many protectors in the party -- which would all be exempt from prosecution -- any abolishment trial would be doomed to fail. In fact, it seems that many of these planted moles are using their immunity and the paycheck from the Verfassungsschutz to actually help the party to survive and thus guarantee their own job security (if the NPD were abolished, the Verfassungsschutz would likely not need as large a staff). In one case, a high member of the NPD stated openly that without being paid from the Verfassungsschutz, he wouldn't have been able to build up the party's branch in his state.
* Reportedly [[http://en.wikipedia.org/wiki/Anne_Bonny Anne Bonny]], a pirate famous for disguising herself as a man, once became attracted to another pirate on her crew. She revealed her secret to the pirate and tried to flirt with him at which point she was shocked to discover that said pirate was [[http://en.wikipedia.org/wiki/Mary_Read Mary Read]], ''another'' pirate famous for being a woman disguised as a man. This was rather awkward to say the least. Although it's alternately claimed that Bonny knew all along that Read was a woman, and only Bonny's lover (and captain) Calico Jack Rackham was fooled.
* An undercover cop arrests a man for selling drugs... who turns out to be [[http://metro.co.uk/2009/07/21/undercover-cops-arrest-undercover-cop-288727/ another undercover cop from a different agency]].
* UsefulNotes/TheStasi had so many people on its payroll (and ''millions'' more that weren't but did it anyway - the so-called "inofficial co-workers") that most people in UsefulNotes/EastGermany were either spied on, spying on someone or ''both''. Most likely this was entirely deliberate, because nothing ensures compliance like the ([[ProperlyParanoid justified]]) belief that someone is always watching you.
* As with much humor, the ''Onion'''s article about KKK infiltrators above is based on the truth. At one point, the KKK (gradually discovered to be a dwindling and impoverished group with little real power or influence) had so many infiltrators that a common joke in spy agencies (and later in the general public) went: "How do you know who the infiltrators at a Klan meeting are? They're the ones who always ''pay their dues''."
* [[https://www.upi.com/Undercover-Detroit-police-attempt-to-arrest-each-other-in-embarassing-drug-bust/8361510804710/ "A group of undercover Detroit police posing as drug dealers tried to arrest another group of undercover police posing as drug buyers in a mishap that resulted in a brawl between more than two dozen armed officers."]]