History Main / HumanOutsideAlienInside

* Some aliens in Comicbook/{{Empowered}}'s verse have two left kidneys. And one kind of alien (maybe the same one) has kidney equivalents that filter the bloodstream using coherent light - essentially, FrickinLaserBeams.

* The [[OurHomunculiAreDifferent Homunculi]] in the manga and 2009 anime of ''{{Manga/Fullmetal Alchemist}}''. They look human, possess skeletons and muscle systems, but they have no internal organs. Instead, they all have a Philosopher's Stone at their core. This gives them the power to [[HealingFactor heal]] from even [[FromASingleCell small pieces of body tissue]] as long as they have souls to draw power from. Many of them have been alive for centuries. Each Homunculus also [[AbsurdlySharpClaws has]] [[ExtremeOmnivore a]] [[{{Shapeshifter}} uni]][[UnlimitedWardrobe que]] [[MadeOfDiamond power]] [[SuperSpeed of]] [[MagicalEye their]] [[CastingAShadow own]]. They're all recognizable by the Ouroboros tattoos they each have somewhere on their body.

* A fairly subtle example: In the ''Literature/ConfederationOfValor'' series, [[OurElvesAreBetter Taykans]] become mature physically, sexually, and (to a limited extent, at least) socially long before they become fertile.

* Mutant powers in the Marvel universe with on occasion be cursorily explained with physiological differences. Mutant psychics will be said to have different brain structures, while mutant speedsters like Quicksilver or Whirlwind will have explanations detailing the RequiredSecondarySuperpower needed to survive their speed; the latter even being said to have body fluids that are thick like motor oil.

* Mutant powers in the Marvel universe with on occasion be cursorily explained with physiological differences. Mutant psychics will be said to have different brain structures, while mutant speedsters like Quicksilver or Whirlwind will have explanations detailing the RequiredSecondarySuperpowers needed to survive their speed; the latter even being said to have body fluids that are thick like motor oil.

** Eldar are also a lot more inhuman than their appearance would suggest. Physically they look like [[SpaceElves tall pointy-eared humans with almond-shaped eyes]], but their musculature is somewhat different (making them stronger than their lithe appearance might suggest), their reflexes are far superior to human ones, and they experience emotions far more strongly than humans do. Eldar pregnancy also lasts much longer than humans (exact length is not mentioned, but it's implied to be several years). According to ''Xenology'' (a background book which contains reports of autopsies of several different alien specimens, written from an in-universe point of view), Eldar internal organs also differ from human ones, their skeleton is of entirely different composition (being more flexible and plastic-like than human bones), their droppings are crystalline, they have no conventional teeth but instead have serrated pieces of jawbone not unlike some species of birds, and their DNA is composed of two entwining double helixes. Also, [[FantasticArousal their ears may be erogenous zones]]. However, ''Xenology'' is not the most reliable source, and much of what is written in it is directly contradicted by other sources.

* No matter the race of the Dragonborn from Skyrim, everything about them on a metaphysical level is a fire breathing, flying lizard. This allows them to pull off feats that horrify mortal and dragon alike.

** Another multiple-personalitied alien race are described by Diane Duane in ''Literature/SpocksWorld''; they have "octocameral" brains, so they have eight personalities each.

* A similar example is [[http://www.pbfcomics.com/?cid=PBF051-Zarflax.jpg this]] ''ComicStrip/ThePerryBibleFellowship'' comic.

* ''WesternAnimation/StevenUniverse'': The Gems are an extreme case of this. Aside from skin, hair, and body colors [[AmazingTechnicolorPopulation based on their namesake jewel]] and a gemstone sticking out of part of their body, they would look perfectly human, with [[FloatingLimbs only]] [[{{WingedHumanoid}} a]] [[{{Cyclops}} few]] having more nonhuman features. However, the only real part of their body is their [[HeartDrive Gem]]- every other part of them is simply a HardLight hologram created for the sake of interacting and walking around. [[TheAgeless They don't physically age]], can [[FusionDance mix their projected forms together with other members of their species]], and [[TheNeedless don't need to eat, breathe, or sleep]]. Temperature also fails to affect them outside of extremes — and even then, certain individuals can ''swim in lava''. If their body projection gets too severely damaged, [[DeathIsCheap they will simply retreat to their gem and reform later]], only a crack in their gem can seriously incapacitate their projected form, but it can easily be healed by Steven and Rose, and the only thing that actually comes close to killing a gem is to shatter them, and even then, [[AndIMustScream their gem shards can still form as incomplete, mindless body parts]]. Also played with, as the Crystal Gems deliberately made their bodies so internally human-like as to include organs that they don't actually need (otherwise they appear to have ''no'' internal organs at all).

* ''WesternAnimation/StevenUniverse'': The Gems are an extreme case of this. Aside from skin, hair, and body colors [[AmazingTechnicolorPopulation based on their namesake jewel]] and a gemstone sticking out of part of their body, they would look perfectly human, with [[FloatingLimbs only]] [[{{WingedHumanoid}} a]] [[{{Cyclops}} few]] having more nonhuman features. However, the only real part of their body is their [[HeartDrive Gem]]- every other part of them is simply a HardLight hologram created for the sake of interacting and walking around. [[TheAgeless They don't physically age]], can [[FusionDance mix their projected forms together with other members of their species]], and [[TheNeedless don't need to eat, breathe, or sleep]]. Temperature also fails to affect them outside of extremes — and even then, certain individuals can ''swim in lava''. If their body projection gets too severely damaged, [[DeathIsCheap they will simply retreat to their gem and reform later]]. Also played with, as the Crystal Gems deliberately made their bodies so internally human-like as to include organs that they don't actually need (otherwise they appear to have ''no'' internal organs at all).

* ''WesternAnimation/StevenUniverse'': The Gems are an extreme case of this. Aside from skin, hair, and body colors [[AmazingTechnicolorPopulation based on their namesake jewel]] and a gemstone sticking out of part of their body, they would look perfectly human, with [[FloatingLimbs only]] [[{{WingedHumanoid}} a]] [[{{Cyclops}} few]] having more nonhuman features. However, the only real part of their body is their [[HeartDrive Gem]]- every other part of them is simply a HardLight hologram created for the sake of interacting and walking around. They don't physically age, can [[FusionDance mix their projected forms together with other members of their species]], and don't need to eat, breathe, or sleep. Temperature also fails to affect them outside of extremes — and even then, certain individuals can ''swim in lava''. Also played with, as the Crystal Gems deliberately made their bodies so internally human-like as to include organs that they don't actually need (otherwise they appear to have ''no'' internal organs at all).

*** The episode "Two Days & Two Nights" brought us the second encounter with [[VoluntaryShapeshifting shape shifting]] aliens. Also a SugarWiki/{{Funny Moment|s}}:

* On the short lived NBC series ''Series/SomethingIsOutThere'', the alien Ta'ra has a number of physiological differences: caffeine was an inebriant, and hands were apparently primary erogenous zones. Additionally, she felt the need to sleep in the nude and at one point became sexually aroused watching ''Crime Story''. The latter two ''may'' have been more cultural than physiological, however.

* The ''Literature/StarfleetCorpsOfEngineers'' stories do this while fleshing out the Ardanans, who were established in ''Series/StarTrekTheOriginalSeries'' as looking just like humans (as did many of the series' aliens). The SCE stories describe the Ardanan brain and demonstrate that its structure and chemistry is very different from that of humans; this becomes a plot point.
** Another Franchise/StarTrekNovelVerse story, ''Literature/ASingularDestiny'', mentions that Zaldans (who look human other than their webbed hands) have a different internal layout.

* ''WesternAnimation/StevenUniverse'': The Gems are an extreme case of this. Aside from skin, hair, and body colors [[AmazingTechnicolorPopulation based on their namesake jewel]] and a gemstone sticking out of part of their body, they would look perfectly human, with [[FloatingLimbs only]] [[{{WingedHumanoid}} a]] [[{{Cyclops}} few]] having more nonhuman features. However, the only real part of their body is their [[HeartDrive Gem]]- every other part of them is simply a HardLight hologram created for the sake of interacting and walking around. They don't physically age, can [[FusionDance mix their projected forms together with other members of their species]], and don't need to eat, breathe, or sleep. Temperature also fails to affect them outside of extremes — and even then, certain individuals can ''swim in lava''. Also played with, as the Crystal Gems deliberately made their bodies so internally human-like as to include organs that they don't actually need.

* Starfire of the ''WesternAnimation/TeenTitans'' (at least, the TV show). Aside from her decidedly orange skin and her ability to fly and to shoot energy from her hands and eyes, she has nine separate stomaches, an oft-unused [[OverlyLongTongue long, prehensile tongue]], a temporary but extensive {{Metamorphosis}} triggered by puberty, and [[KryptoniteFactor a nasty allergy to metallic chromium.]][[note]]metallic chromium is used extensively in metallurgy on this planet from alloying to plating. At minimum Starfire couldn't get within a hundred feet of a car, [[WildMassGuessing unless it's just N allergenic in powder form, like dander]][[/note]]

* Played with in Franchise/{{Tron}}. Programs and Isos resemble humans. Even more specifically for Programs is that they sometimes are a doppelganger for the human who coded them. But when they are wounded, it looks like hunks carved out of their bodies, scars resemble dead pixels on a monitor, and serious or lethal wounds cause them to shatter like safety glass instead of bleed. They feed by drinking energy, and it's implied that their [[TronLines circuitry]] is very sensitive.

* In Zenna Henderson's sadly-underrated short story ''Subcommittee'', Earth is invaded by [[PettingZooPeople fuzzy]], [[AmazingTechnicolorPopulation brightly-hued]] HumanoidAliens. After a huge war in space, representatives from each side begin peace talks. The humans are appalled when the aliens appear to be asking for all of Earth's oceans. Naturally, [[spoiler: it's the wives of two of the chief negotiators, plus their adorable sons, who discover the truth that leads to peace. It turns out that the aliens have become infertile due to lack of a vital nutrient...which is revealed to be ''salt''.]]

[[quoteright:350:[[Series/DoctorWho https://static.tvtropes.org/pmwiki/pub/images/Doctor_hearts_6313.jpg]]]]
[-[[caption-width-right:350:Image by euclase. Used with permission.]]-]

** Despite the Cat appearing to be mostly humanoid aside from his obvious feline teeth, he is said to have six nipples, colour-coded organs and his heartbeat performs it's own rumba, making it "much cooler" than a humans.
** Also inverted, in the episode DNA. They encounter a three-headed, very alien-looking corpse, but said corpse has a wallet containing credit cards and [[{{Zeerust}} a video club membership card]]. The corpse is a human who over-used a machine that messes with the subject's DNA while - somehow - leaving the mind and personality intact. So Alien Outside, Human Inside.

** In [[Recap/DoctorWhoS30E7TheUnicornAndTheWasp "The Unicorn and the Wasp"]], the Doctor recovers from cyanide poisoning by ingesting a variety of different ingredients and shocking himself — the biological TechnoBabble was actually vaguely in the right area for curing cyanide poisoning. "Smith and Jones" also has him survive radiation poisoning from an X-ray by expelling it all through his foot. He also states that Time-Lords are immune to most forms of ionizing radiation and he used to play with Roentgen bricks in his nursery.

* On ''WesternAnimation/{{Ben 10}}'', Osmosians look externally like humans, but have the ability to absorb matter and energy, as well as minor degrees of super strength and durability, which increases when they do. Though to them, pure energy is a GRatedDrug that drives them insane if they absorb too much of it (though this is reversed if the energy is discharged). Also, Osmosians can live much longer than humans and those who live for hundreds of years grow horns. Of course to be fair, in [[WesternAnimation/Ben10Omniverse Omniverse]] we find out that [[spoiler: "Osmosians" look as human as they do because they ''are'' humans, just mutated a bit, and Aggregor, the only member of the "species" to have horns was artificially created.]]

** This trope is directly mentioned in [[Recap/DoctorWhoS12E4GenesisOfTheDaleks "Genesis of the Daleks"]]. A [[MeaningfulName Kaled]] scientists scoffs at the Doctor and his companion's claim that they're not from the planet Skaro. Then their test results come back, leaving the scientist stunned that, despite external appearances, their biology matches nothing native to Skaro.
** Kaleds themselves looked like dark-haired, dark-eyed humans on the outside. However, they had fewer ribs than humans in a more widely spaced ribcage, greenish copper-based blood, purple body tissue, thick lungs, and grey cardiac muscle.

** The very rare inversion did happen once: in [[Recap/DoctorWhoS14E2TheHandOfFear "The Hand of Fear"]], Sarah Jane shakes off a "lethal" poison, as it turns out not to be lethal to ''Homo sapiens''.

** The Fifth Doctor claims that he wears the celery because it's an excellent restorative.
*** He also claims that it will turn purple in the presence of certain gasses that are toxic to him.
*** The Eleventh Doctor asks for celery after a Silurian disinfection attempt.

*** The Dalek in [[Recap/DoctorWhoS27E6Dalek "Dalek"]] apparently specifically needed DNA from a time traveler in order to regenerate itself (and its casing), implying that time travel does something to DNA that makes it categorically different.

* In ''Series{{Roswell}}'', Max gets drunk with just a "little sip" of an alcoholic beverage in about two seconds, and gets back to his sober self without a memory of what he did, or any apparent hangover once he kisses Liz (or might have just been a coincidence). Michael, on the other hand, didn't get drunk the same way, but he got a sort of allergic reaction which made him have electrical lines running through his body, and every sense in overdrive. He did have a hangover. And although their biology is rather human except for their cells, it is said they can sustain a one hour climax, even if they don't go into details about how that exactly happens...

->'''Kim:''' I've got to be honest, I wasn't expecting something so different.
->'''Tal:''' Neither was I. Our species look so similar...well at least on the surface.
->'''Kim:''' I would've never guessed when it came down to the basics. Well, let's just say the birds and bees will be very confused.

* ''Franchise/StarTrek'' likes doing this. A typical Vulcan has a much larger "nonhydraulic" heart located where a human has his liver, copper-based green blood (based on hemocyanin, the copper-based blue-green blood found in a number of real world mollusks and arthropods), nictating membranes in his eyes, a body temperature over 105 degrees Fahrenheit, and a standing pulse rate of over 200. And [[MateOrDie Pon Farr]] as well. Klingons have evolved truly complex redundant biologies, making them next to invulnerable, though prone to many minor malfunctions. They also have [[AlienBlood thick, pink blood]], though we have seen otherwise, including in the theatrical version of ''Star Trek VI'', which introduced the idea (video releases restored a scene showing that the red-blooded Klingon was really a human wearing a mask). There are certainly others.
** The Trill are (two or) three species with separate degrees of this. The Trill symbionts are alien slugs that live for millennia. The humanoid Trill are, conveniently, fitted with a womb-like pouch inside the body that can bond with the symbiont Trill. When bonded, a Trill composed of a symbiont and a humanoid host now have one mind and one personality, to the extent that they are legally a brand new species. How the two species ever figured out that this could be done (it's not exactly the most obvious thing you'd think to do when meeting another intelligent life form) is unclear.
** Betazoids, despite [[HumanAliens looking entirely human]] (apart from their black irises), have an extra lobe in their brain to account for their [[PsychicPowers telepathy]].
** [[Series/StarTrekEnterprise The Denobulans]] have a distinct mating season (when the males fight for mates) and hibernation period. They also can puff up their heads like blowfish to scare predators.
*** Phlox's bizarre biology was an ongoing joke in the series. He has striped toenails that grow so rapidly they have to be cut once a week, a 16-inch tongue that needs regular scraping and a smile that [[http://img.trekmovie.com/images/PhloxSmiling.jpg the Joker would envy]]. Plus he [[HeavySleeper hibernates five to six days a year]].
*** Rajiin is an Oran'takun with the ability to do a complete biometric scan of someone, then wipe their memory of the event, though it's possible some of these abilities have been surgically implanted.
*** The episode "Two Days & Two Nights" brought us the second encounter with [[VoluntaryShapeshifting shape shifting]] aliens. Also a SugarWiki/{{Funny Moment|s}}:
--->'''Trip:''' You think this is my fault?!
--->'''Malcolm:''' You were willing to follow two strange aliens into a basement.
--->'''Trip:''' Gorgeous aliens! Don't forget they were gorgeous.
--->'''Malcolm:''' They were ''male''!
--->'''Trip:''' [[UnsettlingGenderReveal Not at first!!!]]
** In the ''Series/StarTrekVoyager'' episode [[InterspeciesRomance "The Disease"]], Harry Kim has sex with a woman who looks human (as mentioned in the title quote) but prolonged sexual contact makes his skin glow, as well as making the two become physically addicted to each other.
** Pregnant Bajorans have sneezing fits instead of morning sickness. And a complex network of veins bonds the mother to the child, which was the reason for why Nerys couldn't give the embryo back to Keiko (ItMakesSenseInContext).
** The freaking ''Ocampa''. Lifespan of nine years. Body temperature around 16 degrees Celsius. Can only have one child. When ready to mate, they exude a yellow substance from their hands and must have an hour long foot massage with 50 hours of the substance appearing to enable mating. Give birth standing up, from a sack between their shoulders. While their psychic powers probably helped, one still wonders how a species with such a bizarre, and mathematically troublesome, method of reproduction could have come about in the first place.
** A Starfleet officer on ''[[Series/StarTrekDeepSpaceNine DS9]]'' named Vilix'pran (whose species has not been shown on screen) "budded" many children. Who had wings that had to be kept from tangling. Oh right, Vilix'pran takes the pronoun [[MisterSeahorse "he"]].
** When Quark and his family were accidentally sent to 1947 Roswell, we learned that Ferengi biochemistry is sufficiently different from our own that sodium pentathol injections do nothing besides making them very sore at the injection site. Ferengi also have four-lobed brains, which somehow makes them immune to telepathy.
** This is done with ''humans'' in the episode 'The Communicator' when Archer and Reed are captured on a pre-warp planet who initially think they are spies; when medically examined, the aliens comment on their "redundant renal organ" and "red blood with haemoglobin based on iron, a toxic element" and that they are missing four vertebrae. However, their captors assume that Archer and Reed are genetically engineered SuperSoldiers rather than aliens.
*** It also helped expose Riker in 'First Contact' (the episode). Alien doctors examining an unconscious Riker are surprised to find his heart where his digestive tract should be, among other things.

** Pak'ma'ra are carrion eaters, with prehensile Cthulhu-esque tentacles on their faces used for drawing in food. Under the tentacles is a beak, and they require translators to speak to other races. Also, according to the doctor in Crusade, they are not sexually compatible with humans.
--->'''''Captain Gideon:''' [[HeadTiltinglyKinky It's an amazing thing, technology.]]''
* Time Lords from ''Series/DoctorWho'' have two hearts with a redundant circulatory system, a low body temperature, a respiratory bypass system, an ability to regenerate from death twelve times, a lifespan of potentially hundreds of years per body, and a complete additional sensorium tuned to temporal events. The show never addressed how the Coal Hill School nurse failed to notice that Susan was not human.
** This trope is directly mentioned in ''Genesis of the Daleks''. A [[MeaningfulName Kaled]] scientists scoffs at the Doctor and his companion's claim that they're not from the planet Skaro. Then their test results come back, leaving the scientist stunned that, despite external appearances, their biology matches nothing native to Skaro.

** Meanwhile, in ''The Dominators'', the Dominators scan the Doctor's companion believing him to be a native of the Alien Planet of the Week. A later scan of an actual native reveals a totally different anatomy, which backs up the Doctor's earlier lie that there are two intelligent species on the planet.
** The very rare inversion did happen once: in ''The Hand of Fear'', Sarah Jane shakes off a "lethal" poison, as it turns out not to be lethal to ''Homo sapiens''.
** In ''The Daemons'', the Doctor claims that an aspirin might kill him, though it's not clear whether he actually means it, or is just contriving a possible example of why human medical advice does not apply to him.
*** And even assuming he was telling the truth about his reaction to aspirin, it's not clear if this is true for all Time Lords, or if it's just that The Doctor is severely allergic to it.

** In TheMovie, the Seventh Doctor is shot three times in total, in the shoulder and the leg; dialogue makes it clear that these were not fatal wounds. The issue is that the medical team don't understand the Doctor's alien biology, think he's fibrillating wildly out of control due to his (for a human) incredibly high pulse rate of 300 beats per minute, and place a surgical probe in his circulatory system to try to find out why. Unfamiliar with the circulatory system of an alien with two hearts, the probe gets lost, damages the Doctor's body, causes him to have a seizure, and the doctors' panicked attempts to remove the lost probe and revive the Doctor kill him. The Doctor's regenerative process is inhibited by the anaesthetic for several hours (the Doctor himself conjectures that this is why he has amnesia for several more hours following his regeneration), and the scene in the operating theatre makes it clear that the medical staff are also surprised by ''how much'' anaesthetic it took to knock the Doctor unconscious.
** In "The Unicorn and the Wasp", the Doctor recovers from cyanide poisoning by ingesting a variety of different ingredients and shocking himself - the biological TechnoBabble was actually vaguely in the right area for curing cyanide poisoning. "Smith and Jones" also has him survive radiation poisoning from an X-ray by expelling it all through his foot. He also states that Time-Lords are immune to most forms of ionizing radiation and he used to play with Roentgen bricks in his nursery.

*** The Eleventh Doctor asks for celery after attempted anaesthetic from a Silurian.
** When the Tenth Doctor regenerates into the Eleventh, the regeneration causes some sort of biochemical imbalance that the Doctor is trying to counteract by eating various foods. Finally fish fingers dipped in custard do the trick.
** In "Cold Blood", a Silurian attempts to subject the Doctor to a procedure meant to remove surface bacteria that are indifferent to humans but potentially dangerous to their colony. The Doctor suffers considerable pain from the process, and would die if it weren't called off.
** Humans who spend a lot of time exposed to time travel acquire immunities to certain time travel phenomena. There is an implication that the Doctor's companions are slightly 'changed' after travelling through time due to being exposed to the energies of the TARDIS. An episode of ''Torchwood'' showed that Martha's white blood cells, and who knows what else, had been slightly mutated.
*** The Dalek in 'Dalek' apparently specifically needed DNA from a time traveler in order to regenerate itself (and its casing), implying that time travel does something to DNA that makes it categorically different.
** According to "A Good Man Goes to War", [[spoiler:Amy's daughter, Melody Pond, aka River Song, who was conceived inside the time vortex, has gained the Time Lord trait of regeneration]].
* As the only alien species on ''Series/AlienNation'', the internal parts and biochemistry of the Newcomers are well-documented and used in the story for humor and drama. Some notables:
** Survival in hazardous environments.
** Great physical strength.
** Nerve plexus under the arm; their [[GroinAttack most sensitive area]], a [[OneHitKill key pressure point]] in a deadly Overseer martial art.
*** Regular humans have a fairly major nerve cluster in the same place. Although attacking one won't kill, it can do some damage.
** [[MisterSeahorse Males receive half-formed infants from their mates for further development, like a cross between a marsupial mammal and a seahorse]]. (George Francisco was the first male TV character to give birth on-screen.) Conceiving said infant requires all three sexes to participate, by the way.
** They become intoxicated from [[GRatedDrug spoiled milk]].
** They cannot digest cooked animal proteins, and subsist on raw meats.
** [[KryptoniteFactor Saline water]] dissolves their flesh like acid.
** Two redundant hearts; they can take a ''huge'' bullet in one of them and not stop attacking.
** A frightening, [[SuperPoweredEvilSide monstrous metamorphosis]] triggered by an overdose of a unique narcotic.
** A gland in their neck when implanted into a human inhibits the human aging process (but its removal kills the newcomer). Information buried to prevent genocide in the quest for eternal youth.

* On the short lived NBC series ''SomethingIsOutThere'', the alien Ta'ra has a number of physiological differences: caffeine was an inebriant, and hands were apparently primary erogenous zones. Additionally, she felt the need to sleep in the nude and at one point became sexually aroused watching ''Crime Story''. The latter two ''may'' have been more cultural than physiological, however.

* The WitchSpecies from ''Series/SabrinaTheTeenageWitch'' have some incredibly bizarre biological quirks, far beyond what their magical powers would imply. Possessing certain character flaws can inflict them {{Anvilicious}} pun-based mutations (for example, a witch who acts "spoiled" will start to dissolve into foul-smelling ooze), their magic needs to be extracted and "tuned up" regularly to function properly, and their wedding vows involve exchanging ring ''fingers''.
* Krevlornswath ("Lorne") of the Deathwok Clan of Pylea on ''Series/{{Angel}}'' looks quite humanoid, other than the green skin/red eyes/horns thing. You figure out they're called the "Deathwok Clan" for a reason when Lorne gets beheaded and ''remains alive as long as his body isn't destroyed''.
** Lorne's hulking, bearded mom.
--->'''Lorne:''' I thought Our Lady of the Perpetual Seabreeze was the real deal, till the Divine Miss J. walked right through that door and into my ass. ... which is where my heart is. Physiologically. I could show you an X-ray.
* One of the few alien aliens to appear of ''Series/BlakesSeven'' did a very good job of imitating humans, but reverted back to their original form after being shot. Well, mangled original form, due to being shot and all. Because of this, they could have a definitely non-human thing lying on the floor, oozing goo and gurgling without needing to be able to fit an actor inside.

-->'''Rimmer''': Lister, just because they're aliens, doesn't mean they don't have to go to the little boy's room. Of course, they probably do something weird and alien-esque, like it comes out the top of their head, or something.
-->'''Lister''': Well, I wouldn't wanna sit behind one in a cinema!

* There is only one known alien race in ''Series/TimeTrax'', and they are shown and mentioned in only one episode. The Procardians appear to be your usual HumanAliens without any extenal differences, but have a number of biological oddities about them. They can glow and levitate like the aliens in ''Film/{{Cocoon}}''. Their voices sound ''very'' odd to the point where their vocal cords are incapable of producing human speech (and vice versa), although one attempts to say "Thank you" at one point and it sounds a little HelenKeller. They age in stages, meaning they can look exactly the same for several years before metamorphosing into an older equivalent. Since the change is so sudden, it can be difficult to recognize the same Procardian after one such change. Another bizarre feature is their equivalent to our fight-or-flight response to threat. They raise their arms in a combat-like stance, which fires an energy bolt at the threat. The effect of the bolt (on human, at least) is a coma-like state, which can be "cured" with shock therapy. This reaction is instinctive, as they have no adrenalin. Oh yeah, they also don't wear clothes.
* Most of the aliens in the Franchise/StargateVerse are TransplantedHumans, so they rarely fit this trope, but there are a few aliens that definitely do.

** The unnamed[[note]]in the show, at least; the season 3 sourcebook for the RPG calls them the Ilempiri[[/note]] species to whom BountyHunter Aris Boch belongs ([[Series/StargateSG1 SG-1: "Deadman Switch"]]) looks completely human. However, [[AlienBlood their blood is yellowish green]], and something about their physiology makes them immune to Goa'uld infestation.
* In ''{{Roswell}}'', Max gets drunk with just a "little sip" of an alcoholic beverage in about two seconds, and gets back to his sober self without a memory of what he did, or any apparent hangover once he kisses Liz (or might have just been a coincidence). Michael, on the other hand, didn't get drunk the same way, but he got a sort of allergic reaction which made him have electrical lines running through his body, and every sense in overdrive. He did have a hangover. And although their biology is rather human except for their cells, it is said they can sustain a one hour climax, even if they don't go into details about how that exactly happens...

* In the AudioPlay/BigFinishDoctorWho Companion Chronicle "The Darkening Eye", Adric survives a stab wound to the chest because of his species' HealingFactor and the key little detail that his assailant was aiming for the location of a ''human'' heart. Guess which side of the chest cavity holds an ''Alzarian'' heart?

* Inverted in the 2003 ''[[WesternAnimation/TeenageMutantNinjaTurtles2003 Teenage Mutant Ninja Turtles]]'' series, Baxter Stockman and Oroku Saki [[spoiler:a.k.a. The Shredder]] see a thermal camera image of the Turtles, which looks roughly like a human being's heat signature - only humanoid-turtle shaped. They also sweat. This implies that they have a human-like metabolism. They seem to be Turtle Outside, Human Inside. They also have a full set of teeth, and eat human foods. If you have a turtle, don't give it pizza or Chinese food unless it too is a humanoid mutant. [[RealityEnsues It's not good for them]].
* On ''WesternAnimation/{{Ben 10}}'', Osmosians look externally like humans, but have the ability to absorb matter and energy, as well as minor degrees of super strength and durability, which increases when they do. Though to them, pure energy is a GRatedDrug that drives them insane if they absorb too much of it (though this is reversed if the energy is discharged). Also, Osmosians can live much longer than humans and those who live for hundreds of years grow horns. Of course to be fair, in [[WesternAnimation/Ben10Omniverse Omniverse]] we find out that [[spoiler: "Osmosians" look as human as they do because they ''are'' humans, just mutated a bit, and Aggregor, the only member of the "species" to have horns was artificially created.]]
* An extreme case of this is the Gems from ''WesternAnimation/StevenUniverse''. Aside from skin, hair, and body colors [[AmazingTechnicolorPopulation based on their namesake jewel]] and a gemstone sticking out of part of their body, they would look perfectly human, with [[FloatingLimbs only]] [[{{WingedHumanoid}} a]] [[{{Cyclops}} few]] having more nonhuman features. However, the only real part of their body is their [[HeartDrive Gem]]- every other part of them is simply a HardLight hologram created for the sake of interacting and walking around. They don't physically age, can [[FusionDance mix their projected forms together with other members of their species]], and don't need to eat, breathe, or sleep. Temperature also fails to affect them outside of extremes-- and even then, certain individuals can ''swim in lava''. Also played with, as the Crystal Gems deliberately made their bodies so internally human-like as to include organs that they don't actually need.
* The inhabitants of Mewni from ''WesternAnimation/StarVsTheForcesOfEvil'' are beings from AnotherDimension who look identical to humans from the outside, save for female in the royal family having {{Blush Sticker}}s with unusual shapes (for example, main protagonist Star's are heart-shaped and her mother's are diamond-shaped) which sometimes change to other shapes according to their emotion. Female (it's unknown if it's also the case for males) teenagers will go through a variant of puberty called "Mewberty", which causes them to become boy-crazy and eventually turn into purple-skinned moth people who will attempt to abduct any boy in sight until it passes, at which point they will return to their original form with only small wings as a reminder of the event. Men (a few of whom have been seen shirtless to confirm this) lack the wings. One of them survived decapitation and even had his severed head implanted on the neck of a ''horse'' with no apparent problems, but that might have involved magic.
* Most aliens in ''WesternAnimation/MenInBlack'' are StarfishAliens, but Jeeb's unnamed species is identical to humans in every aspect other than their ability to regenerate any wound including the destruction of the head, so long as they have oxygen.