[[quoteright:319:[[Anime/{{Robotech}} http://static.tvtropes.org/pmwiki/pub/images/ZentradiSpies.jpg]]]]
[[caption-width-right:319:Zentraedi spies [[RealMenWearPink blending]] in [[HumansThroughAlienEyes seamlessly]] and [[{{Crossdresser}} without]] [[CrossCulturalKerfluffle drawing attention.]]]]

->'''Kyle Reese:''' "[[FlawedPrototype The 600 series]] had rubber skin. [[PaperThinDisguise We spotted them easy]], but [[ReplacementMooks these are new.]] [[RidiculouslyHumanRobot They look human... sweat, bad breath, everything.]] Very hard to spot. I had to wait till he moved on you before I could zero him.
->'''Sarah Connor:''' Look... [[GenreSavvy I am not stupid, you know.]] They cannot make things like that yet.
->'''Kyle Reese:''' [[TimeTravelTenseTrouble Not yet. Not for about 40 years]].
-->--''Film/TheTerminator''

When humanity makes an enemy of a non-human race, we ''really'' know how to pick 'em. Not only are they unspeakably powerful, they're also really ugly! Eww! The possibilities are very varied. Maybe the aliens are [[WhatMeasureIsANonCute horrid]], [[ReptilesAreAbhorrent reptilian]] creatures, [[RobotRollCall noisy clanking machines]] or twenty meter tall giants. Of course, being so [[BeautyEqualsGoodness ugly]] and [[WhatMeasureIsANonHuman inhuman]] it's no surprise they've come to [[WeComeInPeaceShootToKill wipe us out]]. Well, the upside for humanity being involved in a (probably losing) war against these creatures is we can at least tell them apart from us humans easily, so they'll never infiltrate our society with spies and saboteurs. That is, until they figure out how to make a MobileSuitHuman, make RidiculouslyHumanRobots, or use PeopleJars to change into human forms.

Which is what they just figured out: they look like us now.

[[RoboticReveal The revelation]] will put the entire cast on edge, because they have just discovered the aliens/robots/monsters have developed a [[GlamourFailure (near)]] perfect {{Masquerade}} or disguise. They aren't PuppeteerParasite, able to take control of specific people or pose as them, just able to pose as a human. They are nonetheless much more dangerous because with enough patience they can now infiltrate ''any'' group.

Expect small groups to [[ParanoiaFuel tear each other apart over mutual accusations of alien-ness]]... just what TheMole wants. For a measure of {{irony}}, the aliens infiltrating humanity to rip it apart from the inside may discover that HumanityIsInfectious... and not in a ''Literature/TheWarOfTheWorlds'' sense.

Most of the ShapeShifter tropes and spy tropes apply, with the caveat that things like KillAndReplace and DeadPersonImpersonation can only be used if few people really knew the original, since the impersonator can't mimic specific people. A trope increasingly beloved by Live Action Series, as it neatly avoids the potential SpecialEffectFailure of making robots, aliens etc... [[CoconutSuperpowers and saves money]] on SpecialEffects.

The trope may be PlayedForLaughs if the non-humans adopt a PaperThinDisguise but still fool people in their persona as "HughMann."

Contrast AFormYouAreComfortableWith, which doesn't involve the aliens deceiving us into mistaking them for humans; and HumanAliens in which the aliens just happened to look like us to begin with. Compare TheVirus. SisterTrope to PuppeteerParasite. A rich source of ParanoiaFuel.

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!!Examples:

[[foldercontrol]]

[[folder: Anime and Manga ]]

* Inverted in ''MartianSuccessorNadesico'', when the Jovians -- frequently referred to as "lizards" for much of the first half of the series and depicted as monstrous nonhumans in government propaganda -- turn out to actually be humans, forgotten colonists from Earth.
* ''{{Robotech}}'' and its parent, ''{{Macross}}'' have the Zentraedi, a race of giants who later reveal they can "micronize" to become our size. They send a team of spies into the SDF-1, which backfires horribly for their PlanetOfHats culture.
** ''GenesisClimberMospeada'', another series adapted into ''Robotech'', has the Inbit/Invid start recreating themselves in humanized forms, starting with one sent to spy on the protagonists.
* In ''KeroroGunsou'', higher-ranked Keronian platoons are authorized to use technology that lets them mimic humans almost perfectly. Unfortunately for Keroro, his Rank F squad is forced to rely on a set of [[PaperThinDisguise dubious robotic suits]].
* The formless JAM in ''SentouYouseiYukikaze''. In the anime, they start by copying Earth's technology (namely weapons and aircraft) before later moving onto human beings themselves.

[[/folder]]

[[folder: Comic Books ]]

* This has always been the approach of the [[VoluntaryShapeshifting Skrulls]], the antagonistic alien race found in MarvelComics, but most of all in the SecretInvasion CrisisCrossover.
** Also, the now-gone [[RomSpaceknight Dire Wraiths]].
* This was eventually used as part of the FantasticRacism angle in Marvel, to better justify the SupernaturalAngst of the ''Franchise/XMen''; mutants got a bad enough rep when they were all believed to be deformed and unsightly, but then the humans figured out that some mutants looked perfectly human whilst having superhuman powers...
[[/folder]]

[[folder: Fan Works]]
* The use of humanisation technology in ''Fanfic/{{Pokeumans}}'' allows transformed Pokeumans to resume their old human forms - but only for a few hours. The PRT use these to rescue transforming Pokeumans before Pokextinction get there.
* In ''Fanfic/MassEffectHumanRevolution'' [[spoiler:the Geth Infiltrator]] disguises itself as a human in order to get into Noveria.
* In {{Vathara}}'s ''[[https://www.fanfiction.net/s/2698347/1/Walk-Through-the-Valley Walk Through the Valley]]'' has a rare heroic version. Hiko's people, the Confederacy, are at war with TheFederation, which insists on tearing its women and children screaming from their homes, battering them and turning them over to the [[HumanSubSpecies merrows]] for a form of MindRape called conditioning, which [[GettingSmiliesPaintedOnYourSoul leaves you]] [[HappinessInSlavery happy to do and be whatever they want to be]]. It's implied that it leaves you without compassion. The reason they take slaves is to restore the genetic diversity they lost when they became chronically inbred because they were such a small, isolated population. They tell themselves that these gene donors are willing. They also do it to Confederate soldiers, who are dropped back into the units they were pulled from to wreak havoc on their comrades. The only way to prevent yourself from becoming conditioned is to temporarily become a LittleBitBeastly with the help of LegoGenetics, which entails government-approved DNA sequences and extremely complicated life-support equipment that no one uses for anything else. Using claws, etc., means modifying the brain. Ensuring that alterants know when to use them means adding instincts from the species used as a source of DNA. This makes alterants easy to spot, no matter how well the alterations are hidden. They cannot make alterants in mind only; volunteers go mad in weeks. This is where the ookamimoya alterants come in. The ''ookamimoya'' are a species of [[{{EMP}} EM]]-sensitive, lupine predators that live very long lives, have few offspring, which they cherish, a pack with which they share a PsychicLink, extreme distrust of outsiders, incredibly durable bodies, InnateNightVision, AlienHair in the form of sensory tendrils with which they pick up emotions and which move on their own; pelt tendrils that don't; and hidden claws. Ookamimoya ''alterants'' will have sensory tendrils on the scalp the thickness of human hair, eyebrows and eyelashes with tendencies of both pelt and sensory tendrils, zero hair or not-hair elsewhere, KaleidoscopeEyes with exotic colors that shift to golden/amber at night/low light conditions, the ability to sense ''ki'', lack of aging, hidden claws and a strong killer instinct that drive them to kill the conditioned.
[[/folder]]

[[folder: Film ]]

* In ''Film/MenInBlack'', the alien {{villain}}s do this, but so do many (relatively) friendly aliens, as it is the only way they can live safely on Earth.
* Ditto ''Film/{{Halloweentown}}''.
* The eponymous robots in ''Film/{{Screamers}}'' started off as small, subterranean weapons; they were deployed on a desert planet torn by war between rival factions. The screamers were produced en masse in an underground, automated facility, which eventually began to develop more advanced models; Type Is were still small robots, but more streamlined. Human models were also developed, including small children, a male adult, and a female adult. Becker, a Type II (adult male), claims he can change his appearance by carving off the faces of humans.
* In ''Film/TerminatorSalvation'', this is the first time they go ''from'' "noisy clanking machines" to "RidiculouslyHumanRobots" in a ''Franchise/{{Terminator}}'' film. Skynet explicitly went through several Terminator design evolutions to do this, reaching the fleshy [[Film/TheTerminator T-800]] and ShapeShifter [[Film/Terminator2JudgmentDay T-1000]] and [[Film/Terminator3RiseOfTheMachines T-X]].
* ''[[TransformersFilmSeries Transformers: Revenge of the Fallen]]'' got a good amount of drama out of having a Decepticon who could pose as a human. As if paranoia about everyday vehicles and devices wasn't enough.
** ''{{Transformers}}'' in general is clearly in the same spirit. While most Transformers disguise themselves as vehicles rather than people,, the principle is the same... Any car on the road or plane in the sky could be a robot in disguise. One of them could be in your driveway ''right now''. And that's just the rank and file; it's been shown that they've branched out and there are Transformers who are capable of becoming all sorts of things you might have ''insude'' the house as well, like a camera, a microscope, a wristwatch, or a computer not terribly different from the one you're looking at right now. That monitor you're staring into? It could be ''staring back''.
* Inverted in ''Film/{{District 9}}'', when the young alien remarks that [[spoiler:Wikus, in the process of transforming into an alien,]] "looks the same" as him. Also a CrowningMomentOfHeartwarming.
* ''Film/{{Mimic}}'' was basically about this -- the giant mantis/termite hybrids may not have a perfect disguise, but if you're in poor lighting and not paying attention, they look a ''lot'' like a tall man in a trenchcoat.
* Referenced in ''Film/BackToTheFuture'', though of course Marty [=McFly=] is perfectly human.
-->"It's already mutated into human form!"
* The entire premise of ''Film/TheThing1982'' and ''Film/TheThing2011'', played for all the ParanoiaFuel it's worth.

[[/folder]]

[[folder: Literature ]]

* PhilipKDick did several straight versions of the premise (''Screamers'', mentioned above, is based on one of his stories), as well as a parody: in "The War with the Fnools", the Fnools are capable of an almost-perfect human disguise, but are still pretty easy to spot, because (a) they usually travel about in groups, all wearing the same disguise, and (b) they're only two feet tall.
* Creator/TerryPratchett has the Auditors do this in ''Discworld/ThiefOfTime'': one takes the form of a woman much of the time in order to ensure the building of a glass clock that will stop time (and thereby make their job much tidier). When she starts acting too human, teams of other Auditors join her to ensure that it gets completed and started -- while keeping her, and each other, under control.
* Clifford D. Simak has a group of aliens ''buying'' the Earth in his novel ''They Walked Like Men.'' The aliens were shape-shifters, capable of becoming anything at all -- a human, an automobile, a pile of paper currency... Their default shape? Bowling balls. (Well, they ''looked'' like bowling balls, anyway.) To shift into something larger than their natural size, multiple aliens merged and changed shape.
* ''[[{{Goosebumps}} Calling All Creeps]]'' is pretty much based around this concept.
* Pops up several times in ''Literature/{{Animorphs}}'', where the controllers suspect a human of being an Andalite in morph.
* The Mokuls who have infiltrated Earth in K. H. Scheer's ''Der Verbannte von Asyth'' (trans. ''The Exile from Asyth'') explicitly use masks to disguise themselves as human and study prospective targets for quite a while before replacing them. (They also tend to keep the kidnapped originals alive in order to pump them for more information.) The eponymous protagonist and his companion, on the other hand, belong to a species of HumanAliens to begin with -- though as it turns out their ''fingerprints'' aren't anywhere near human, and they have a few other peculiarities (like [[AlienCatnip the effect coffee has on their metabolism]]) that end up giving them away.

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[[folder: Live Action TV ]]

* The TropeNamer is ''Series/BattlestarGalacticaReimagined''. The Cylons have evolved from "walking chrome toasters" into {{Artificial Human}}s. The opening and a few characters use the line, and it ''does'' cause a lot of mistrust among the human survivors.
** [[Series/BattlestarGalacticaClassic Galactica 1980]] beats them by twenty-odd years by having human-form cylon robots in the episode "The Night The Cylons Landed". However, the ones on the reimagined series are completely human looking, down to having [[RidiculouslyHumanRobots a reproductive system.]]
* This is used from time to time on ''Franchise/StarTrek'', usually as a result of MagicPlasticSurgery, but other examples include the appropriately named shape-shifters from ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'', and Species 8472 in its final appearance on ''Voyager''. Inverted on an episode of ''Series/StarTrekTheNextGeneration'' where the Romulan proconsul correctly surmises that TheFederation is using Romulan-looking spies.
** Also used in an episode of [[Series/StarTrekTheOriginalSeries The Original Series]], combined with HumanityIsInfectious.
** This trope is outright exploited by the Founders in ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'': One reveals himself to [[TheCaptain Sisko]] to gleefuly reveal that there are only three Founder infiltrators on the ''entire'' planet Earth, center of TheFederation, and look what they've accomplished! [[spoiler: In fear of the possibility of Founder infiltrators amongst them, Earth declares martial law, and a series of events nearly leads to an outright military coup of the civilian government, and two Starfleet ships [[FriendOrFoe firing on each other]].]]
* The human-form Replicators in ''Series/StargateSG1''. A different group of bad guys try to invoke this with a friendly species that create illusions and fake memories in the minds of potential hostiles as a self defense mechanism.
* ''{{V}}'' has reptilian aliens.
** Played both ways, as not only have the Vs infiltrated human society, there is a [[LaResistance rebel faction]] which sympathizes with humankind and seeks to thwart their leader's plot. It's revealed that these rebels have even infiltrated the upper echelons of the V command structure.
* This is by far the most significant difference between the ''Literature/TheWarOfTheWorlds'' film/radio show/whatever and the later [[Series/WarOfTheWorlds TV show]] -- in the latter, the Martians are able to [[KillAndReplace posess human bodies at will]].
** The second season implements the same trope, but in a radically different way: the second wave of aliens have altered their biology to the point that they now look outwardly human (Albeit with luminous blood)
* The nine foot tall, eight hundred pound Reptilian monsters with whom Humanity fights a losing war in a couple of epsiodes of the revival of ''Series/TheOuterLimits'' manages to pull this off by surgically-altering their (much smaller) females.
* The Skins on ''{{Roswell}}''.
* Every alien except Cole and Zin on ''Tracker''
* All the aliens in ''Series/TheInvaders''.
* Parodied (with particular nods to ''BattlestarGalactica'') in a sketch on ''Series/ThatMitchellAndWebbLook''. In the midst of a RobotWar, a rumour spreads that robots have infiltrated the space station, and are supposedly indistinguishable from humans. Cut to a particularly clunky TinCanRobot, talking to several other people (in textbook RoboSpeak) who seem to be under the impression he's human. Even when a slice of toast pops out of him.

[[/folder]]

[[folder: Tabletop RPG ]]

* ''TabletopGame/CallOfCthulhu''.
** The Mi-Go can surgically modify themselves to fit inside a "human suit" and masquerade as people.
** The said 'suits' are made by hollowing out a human body, by the way.
** Serpent People can use spells (such as Body Warping of Gorgoroth) to take human shape.
* In {{Traveller}} there is an interesting twist. When the Terrans meet the Vilani they learn that they actually ''are'' human. Of course that does [[HumansAreBastards not necessarily make the meeting pleasant]].

[[/folder]]

[[folder: Web Comics ]]

* ''PartiallyClips'' parodied this [[http://www.partiallyclips.com/index.php?id=1633 once]].
* In ''Webcomic/GirlGenius'', [[BrainwashedAndCrazy "revenants"]] were initially known to the ''characters'' by obvious mindlessness and a ZombieGait. The ''readers'' have known almost since meeting the first one that some act perfectly normal until they receive an order, which came as a nasty shock when they were found out.

[[/folder]]

[[folder: Western Animation ]]

* ''WesternAnimation/RoughnecksStarshipTroopersChronicles'' had the Imposter Bugs (a subspecies that could fit inside the Mobile Infantry's PoweredArmor to evade detection), and later the Infiltrator Bugs (full-on shapeshifting in and out of human form).
* ''WesternAnimation/TheFlintstones'': "Ten Little Flintstones" has an alien ship landing in Bedrock and creating a series of Fred clones to learn about Earth prior to a pending invasion. The clones simply march around smiling vacantly and saying [[CatchPhrase "Yabba-Dabba-Doo"]] ad infinitum, and everyone thinks each is actually Fred.
* ''TomTerrific'': The story arc "Million Manfred Mystery" dealt with some impressionable aliens who mistake Mighty Manfred the Wonder Dog to be Tom (he's wearing Tom's funnel cap while he's off at the store), so they make a plan sheet of Manfred and the entire alien race duplicate themselves as Manfred. The base reason is that Tom is so likeable that the aliens want to be just like him so Earth people will like them as well.

[[/folder]]

[[folder: Video Games ]]

* ''VideoGame/StarCraftIIHeartOfTheSwarm'' adds a (multiplayer-only) Zerg unit called the Changeling, which upon entering sight range of an enemy unit automatically changes its color and transforms into that enemy's tier 1 unit (Terran marine, Protoss zealot, or zergling). Since it can't attack and has no other abilities, this is only useful for scouting.
* A recurring theme in ''VideoGame/SuperRobotWarsOriginalGeneration''. Even when not deliberately trying to disguise themselves, most of the alien monsters they fight seem to get [[BishonenLine progressively more humanoid]] [[SortingAlgorithmOfEvil as the game goes on]]. Actually inverted with the two main alien factions, though, similar to the Nadesico example. One turned out to be human abductees brainwashed by an alien MasterComputer, the others (& by extension the creators of the aforementioned computer) were actually descendants of a lost starfaring civilization from Earth. Played straight by the {{Eldritch Abomination}}s known as the Einst, however, who can create copies of people they've encountered & whose supposed Ultimate Lifeform is an enhanced clone of one of the main characters.
* Midway through ''VideoGame/{{Marathon}}'', the Pfhor begin fielding ActionBomb simulacra that blend in with the [[RedShirt Green Shirts]]... Except for their (mostly) [[CloudCuckooLander strange exclamations]] and AlienBlood.
* In ''CityOfVillains'' you can contact Kelly Uqua, who is working for [[MegaCorp Crey Industries]]. There's a nasty rumor floating around that the real Uqua is dead, and a Rikti alien can alter its form to match hers. Kelly wants you to enter one of Crey's warehouses and delete this report. Kelly also occasionally slips into the Rikti's VerbalTic while talking to you. A separate ''CityOfHeroes'' mission has you finding a Rikti who was posing as Kelly, whose [[GlamourFailure transformation machinery has broken down.]]
* In ''VideoGame/XCOMEnemyUnknown'' the Thin Man alien units would count as this. Their disguise is pulled off pretty good as well... thin men! Until they pull out their alien weaponry and start doing back-flips in business suits that is. Also their eyes if studied are reptilian in nature. Which would explain why they wear dark glasses.
* ''[[VideoGame/TheThing The Thing 2002]]'' has this as a gameplay mechanic. By using a syringe and a chemical that reacts to blood by releasing heat, you can test your party members for infection. If the syringe changes from red to brown, they're A-O-K, but if the syringe breaks, fry him, he's an alien, and mutating into a beastie as we speak.

[[/folder]]
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