->"He was a candidate for a Midwestern congressional seat, and he hired me to manage his campaign advertising. Unfortunately, his opponent turned up something in his past with which we could not cope."\\
"Let me guess: he was secretly a liberal."\\
"Worse. An alien."\\
"You're kidding?! An undocumented alien running for--"\\
"No. A space alien, Ms. Walters."
-->--''ComicBook/SensationalSheHulk'' #11, Jan. 1990

A character of extraterrestrial origins. For tropes about what ''makes'' them alien, at least from a biological standpoint, see BizarreAlienBiology.

[[Film/{{Aliens}} If you thought it meant "illegal aliens" and signed up]], click RaceTropes. For interspecies romantic or sexual interactions, see the InterracialAndInterspeciesLoveIndex.

If there are no aliens at all, see AbsentAliens.

Compare FantasticSapientSpeciesTropes. Not to be confused with OthernessTropes, though there may be some overlap.
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!! '''Tropes:'''
[[index]]

!!! Levels of the ladder of alien strangeness:
* HumanSubspecies: Aliens who are related to humans.
** TranshumanAliens: A group of aliens are revealed to have evolved from humans.
* HumanAliens: An alien which looks, sounds, and to some extent, acts human.
** HumanOutsideAlienInside: An alien that looks like a human on the surface, but has some wacky parts and whatnot inside their body.
* NotQuiteHuman: An alien that is practically the same as a human except for one difference.
* RubberForeheadAliens: An alien whose face is significantly different from a human's, but only their face.
** GreenSkinnedSpaceBabe: An alien woman who looks like a human except for one or two obvious differences, and who at least one person in the main cast is attracted to if she's not just MsFanservice.
** SpaceElves: Aliens who think they're superior (or might even ''be'' superior in some cases) to us, and act like a fantasy race.
* HumanoidAliens: Aliens who are humanoid, but don't look human.
** FishPeople: Underwater aliens, who are humanoids but look sort of like fish.
** FrogMen: Humanoids that look and act rather like frogs.
** TheGreys: Grey, usually naked, short, humanoid aliens with large heads.
** LittleGreenMen: Short, green aliens who drive flying saucers, and usually have antennae.
** TheReptilians: Aliens that look like humanoid reptiles.
** IntelligentGerbil: An alien that's basically like a sapient, bipedal version of an Earth animal.
*** UrsineAliens: Humanoid aliens similar to bears.
*** CatFolk: Humanoid aliens based on cats.
* AngelicAliens: Graceful aliens that look sort of like humans and are seen as extremely beautiful.
* AlienFairFolk: Aliens that look like fantasy creatures from Earth's folklore (fairies, gnomes, trolls, goblins) or fantasy creatures who pretend to be aliens.
* LittleGreenManInACan: Aliens that you can't tell what they look like as they all wear strange outfits.
* MechanisticAlienCulture: Aliens that are organic, but act like robots and have very tight schedules.
* InsectoidAliens: Aliens based on Earth bugs.
** BeePeople: A race of aliens that have workers, drones and queens like bees.
** BigCreepyCrawlies: Giant bugs.
** InsectQueen: The queen of a race of Insectoid Aliens.
* AlienAnimals: Aliens that look ''exactly'' like Earth animals.
** KillerSpaceMonkey: Aliens that look like monkeys or non-human apes and are evil.
** SpaceWhale: Aliens which look like whales.
* SandWorm: Giant alien worms that live in the desert.
* StarfishAliens: Aliens that are radically different from humans.
** OctopoidAliens: Aliens that look like squids, octopi or jellyfish.
** LivingGasbag: Floating aliens that are literally full of gas.
* MushroomMan: A creature that looks like a cross between a person and a mushroom.
* PlantAliens: Aliens that look like or are partly made of plants.
* BlobMonster: Aliens that resemble shapeless blobs.
* SiliconBasedLife: Aliens that are made of mostly silicon.
* MechanicalLifeforms: A race of robots or cyborgs that are treated as a real species.
* LivingShip: A ship that's alive.
* EnergyBeings: Non-corporeal aliens.
* GeniusLoci: A sentient place.
* SufficientlyAdvancedAlien: Aliens that are so advanced that their technology seems like magic to humans.
* EldritchAbomination: An alien that just makes no sense.

!!! SFX:
* PeopleInRubberSuits: Aliens (usually evil) that wear skin-tight suits.
* {{Muppet}}: A type of puppet like in ''Series/TheMuppetShow''.
* SerkisFolk: Characters created by dubbing an actor with CGI.

!!! Interspecies relations:
* AlienNonInterferenceClause: Humans don't interfere with the development of alien culture because they have a law against it.
* AliensAreBastards: All aliens in a work are evil.
* AliensSpeakingEnglish: Aliens can speak human languages for no reason.
** AliensOfLondon: Aliens who speak English with Earth accents.
* AnatomicallyIgnorantHealing: An alien tries to heal a human but have no idea how.
* AncientAstronauts: Aliens that can travel through space and apparently did things like build pyramids or be mistaken for gods in old times.
* {{Area 51}}: Aliens being hidden in Area 51 (which is a real place, but no aliens are being hidden there in real life that we know of).
* DescriptivelyNamedSpecies: A species that has a name based on their appearance/behaviour.
* FirstContact: Humans meet an alien species for the first time.
* FirstContactFauxPas: A misunderstanding happens during first contact that usually leads to war.
* FirstContactMath: Trying to make first contact by doing math.
* FirstContactTeam: People suspect aliens are around and make a plan with dealing with first contact.
* JustForFun/HowToInvadeAnAlienPlanet: A joke guide for aliens on how to invade Earth or some other planet.
* HumansAreSmelly: Aliens that hate the smell of humans, even if said humans are clean.
* HumansNeedAliens: Aliens which protect humans from different aliens.
* HumansThroughAlienEyes: Aliens who think humans are bizarre.
* HumorlessAliens: Aliens that don't understand humor.
* IComeInPeace: During first contact, one species lets the other know they don't intend to harm them.
** TakeMeToYourLeader: Aliens want to be taken to humans' leader.
** WeComeInPeaceShootToKill: A bad first contact-the aliens come in peace, but the humans try to kill them.
* InnocentAliens: Aliens that are well-meaning and clueless.
* InscrutableAliens: Aliens that we have no idea how to communicate with and don't know much about.
* KlingonsLoveShakespeare: An alien likes a piece of human culture.
* MistookTheDominantLifeform: Aliens want to talk to our pets instead of us.
* PlanetLooters: Aliens robbing us.
* ProtocolPeril: A race of aliens with strict rules that have severe punishments for breaking them, which is bad news if humans are visiting.
* PunyEarthlings: All the aliens have cool powers that we don't.
* TheRightOfASuperiorSpecies: Aliens that think they are superior to humans and therefore allowed to do bad things to them.
* RoswellThatEndsWell: Aliens associated with crashing by Roswell.
* ScaryDogmaticAliens: An evil group of aliens with a strict ideology.
* ServantRace: A race made to serve another.
* SlaveRace: A race of aliens that were enslaved by another.
* StayWithTheAliens: Aliens want to take a human with them.
* SuperiorSpecies: A race of aliens that are somehow superior to humanity.
* ToServeMan: Aliens who try to eat humans.
* WhatMeasureIsAHumanoid: A romance between a human and a non-human humanoid is not seem as {{Squick}}y.
* WhatMeasureIsANonHuman: Humans are seen as the only relevant species.
* TheXenophile: A human who likes aliens.

!!! Reproduction:
* BizarreAlienReproduction: Aliens have sex in a weird way.
* BizarreAlienSexes: An alien species with a weird set of sexes.
* DesignerBabies: A human is genetically modified in utero to make them "better" somehow.
* DyingRace: A race of sentient beings who are dying out.
* ExoticEquipment: Aliens with unusual privates.
* FaceFullOfAlienWingWong: A creature reproduces by impregnating another species (often a human).
* ImmortalProcreationClause: Immortals who can't have babies.
* InterspeciesRomance: A human and a non-human who end up in a romantic relationship.
** BoldlyComing: Sex with aliens.
** DominantSpeciesGenes: Two creatures of different species have a kid that has the traits of the most "dominant" parent.
** {{Gendercide}}: Killing one gender.
** HotSkittyOnWailordAction: Two aliens/monsters of different species have sex, but it begs the question just ''how'' they did it.
** MarsNeedsWomen: A male alien/robot/monster/whatever who's attracted to human women.
** OnlyYouCanRepopulateMyRace: An alien woman whose species is in danger of extinction has to mate with a human male.
* PlanetaryParasite: Parasites that use a whole planet as their host.
* UterineReplicator: Babies are made in a machine instead of a woman's womb.

!!! Genders:
* BizarreSexualDimorphism: An alien race where the males and the females look ''way'' different from one another.
* GenderEqualsBreed: Somebody's species depends on their gender.
* OneGenderRace: A species that's all male or all female.

!!! General tropes and other features:
* AbusiveAlienParents: Aliens are bad parents.
* AlienAbduction: One or more aliens kidnap/s one or more humans.
* AlienAmongUs: An alien living with a bunch of humans and trying to keep their alienness secret.
** HughMann: A human is swapped with an alien impostor who does a terrible job at appearing human.
* AlienArtsAreAppreciated: Art made by one species is appreciated by aliens.
* AlienAutopsy: Humans study dead aliens.
* AlienCatnip: A substance that's fine for humans but affects aliens sort of like a drug.
* AlienEpisode: Aliens visit Earth for one episode.
* AlienHair: List of hairstyles fictional aliens often have.
* AlienInvasion: Aliens try to conquer Earth.
** BenevolentAlienInvasion: Aliens invade but they do the humans well.
** EasilyThwartedAlienInvasion: Humans can easily defeat invading aliens.
* AlienKudzu: A plantlike alien arrives on Earth and starts "seeding".
* AliensAndMonsters: Whenever evil aliens or monsters arrive, the best thing to do, apparently, is destroy them.
* AliensNeverInventedTheWheel: Aliens that have no idea what any technology is, even basic technology.
* AliensStealCable: Aliens learn about Earth from radio and TV.
* AliensStealCattle: Aliens abduct cows and bulls, not people.
* AlternativeNumberSystem: Aliens with a different way of counting than humans.
* AmusingAlien: A funny otherworldly character.
* AnalProbing: Aliens studying humans by [[AssShove sticking things up their butts]].
* BarFullOfAliens: A bar full of many different aliens.
* BizarreAlienBiology: Aliens that work physiologically different from humans in all kinds of weird ways.
* BizarreAlienPsychology: Aliens think a lot differently than humans.
* BlueAndOrangeMorality: A set of morals that are completely bonkers to most humans.
* BrainInAJar: A human brain is kept alive in a jar.
* CameFromTheSky: Aliens fall from the sky and are initially thought to be a meteorite.
* ChestBurster: An alien parasite leaves its host's (usually a human) body by bursting through their chest.
* CropCircles: Large geometric patterns in fields of crops, thought to be (and in some cases, actually) done by aliens.
* DittoAliens: A species of aliens where all the individuals look the same.
* TheDogIsAnAlien: An alien disguises itself as a pet.
* DramaticAlienVTOL: Dramatic music plays when an alien spaceship takes off or lands.
* EldritchStarship: An incomprehensible starship.
* ETGaveUsWiFi: The idea that aliens invented or helped invent some modern technology.
* ExposedExtraterrestrials: Aliens that wander around naked.
* FlyingSaucer: A disc-shaped starship.
* HigherTechSpecies: One alien race is more technologically advanced than the others.
* ImportedAlienPhlebotinum: Humans using alien technology.
* IndoEuropeanAlienLanguage: Non-human languages are based on the languages of their creators.
* InsufficientlyAdvancedAlien: Aliens that don't make sense because they managed to travel to Earth but otherwise seem to have no idea what technology is or how it works.
* KlaatuBaradaNikto: ShoutOut's to the film ''Film/TheDayTheEarthStoodStill''.
* LawOfAlienNames: Common formulas writers use for making names for aliens.
* MarsNeedsWater: Aliens trying to steal water from Earth.
* MarsWantsChocolate: Aliens trying to steal Earth snacks.
* TheMenInBlack: Generic agents, often involved with investigating or denying aliens' existence.
** JustForFun/IfIAmEverHeadOfAnAlienMonitoringAgency: A joke page for how to be the Men in Black's leader.
* MirrorChemistry: References to chirality in aliens.
* MistakenForAliens: One or more people mistake someone or something or a group of people for aliens.
* MoreTeethThanTheOsmondFamily: Monsters with a lot of teeth.
* MulticulturalAlienPlanet: An alien planet with several cultures.
* MyBrainIsBig: A creature with a huge brain.
* NamedAfterTheirPlanet: The name of an alien race is derived from the name of their home planet.
* NoBiochemicalBarriers: Aliens can live on Earth (and humans can live on alien planets) perfectly fine.
* NoSuchThingAsAlienPopCulture: Aliens that have no popular culture.
* NotOfThisEarth: An unknown object or substance is found, analyzed, and revealed to be not from Earth.
* OminousFloatingSpaceship: An enormous alien starship floating above a city without doing much looks foreboding.
* {{Panspermia}}: Creatures on Earth evolved from alien microbes/simple alien animals.
* PeopleJars: People in jars.
* APlanetNamedZok: Planets with rare letters from the Latin alphabet.
* PuppeteerParasite: Alien parasites that take over their hosts' personalities.
* SolidGoldPoop: One species' waste (poop, urine, tears etc) is valuable to another species.
* SpeculativeFictionLGBT: Lots of LGBT+ characters in sci-fi.
* SpiceOfLife: Spices from other planets.
* StarfishLanguage: Aliens speaking a language with weird characters.
* StrongerWithAge: A species that gets stronger as they age.
* TechnologyUplift: Aliens who feel they're responsible for sharing technology with other species.
* TheyLookLikeUsNow: Evil {{shapeshifting}} aliens learn to look like humans.
* TouchedByVorlons: A character gains powers or their powers get enhanced due to interaction with aliens.
* TwoOfYourEarthMinutes: Aliens mention that they are using human time, not their time.
* {{Ultraterrestrials}}: A species that came from Earth, left, and now want to come back.
* UnusualEars: A humanoid with non-human ears.

[[/index]]
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