Human Aliens - Television Tropes & Idioms

alt title(s): Human Alien

Christina: You look human.

The Doctor: You look Time Lord.

— Doctor Who, "Planet of the Dead"

When a creature from a planet other than Earth looks like a human, sounds like a human, acts somewhat like a human and gets confused for a human.

Their internal physiology may well be different, whether a little or a lot, but otherwise they appear to be the genuine article.

In-story, this occasionally leads to a Hand Waving story about how all the races have some common ancestor. Other times, it gets justified by using a Transplanted Humans story. Out-of-story, this is often explained by the fact that there are remarkably few non-humanoids in the SAG or Equity. Other explanations include the idea that a humanoid form is the natural result of any evolutionary path (Humans Are Special on Evolutionary Levels). Recent research may hint at this being true to some extent; many species seem to be engineered by evolution for maximum fuel efficiency. The bipedal human body has remarkable agility and stamina for its size, though there are some notable flaws like weak joints and a narrow birth canal. Although our impressive cognitive abilities and incredibly complex social structure evolved to counter these.

This trope also covers shape-shifters who budget-savingly stay in human form around humans.

In 1950's movies, this also could be used as an actual part of the theme of the story, as the idea that these sorts of aliens could pass completely for humans made a rather handy metaphor for Communism.

The bottom rung of the Alien ladder, below Rubber Forehead Aliens and Intelligent Gerbils. May or may not apply to Fantasy settings, where the characters are either implied or explicitly stated to be human despite the world being obviously not our Earth.

Contrast with Starfish Aliens.

Examples

Anime

To Heart 2 brings us Lucy Maria Misora, aka Ruuko Kireinasora.
The Zentraedi of Macross/Robotech and its descendants are one of the clearer examples of the trope, straight down to the HandWave concerning their origins being linked to that of humanity. The primary physiological difference being that in their natural state they are ten meters tall, but can through an ill-defined process be shrunk down to roughly human size (or expanded back up).
The Buff Clan in Space Runaway Ideon look identical to humans, with the exception of them lacking pupils. They also possess the honor code of the samurai, call their warriors samurai (though the actual humans don't), and even call their home planet Earth. If it weren't for the fact that they were an isolated race before meeting the people of Logo Dau, you'd swear that they were human!
The aliens who inhabit the world of Simoun are all mostly human, except that they're all born female, and half of them change sex at age 17.
- Well, technically they are all born neuter with external female traits, like ant drones, and only get actual gender-properties at the age of 17, namely the ability to procreate, either as males or females.
The natives of The Twelve Kingdoms seem almost indistinguishable from humans of Earth stock, but in fact have a bizarre life cycle that includes being born from large fruit that grows on special trees.
Barring their monkey-esque tails (which can be permanently removed), Saiyans from Dragonball Z look exactly like humans, and can even interbreed with them with ease. Of course, the "Earth" of Dragonball is also inhabited by five foot tall talking foxes, dogs, cats, pigs, sea turtles... and nobody ever thinks any of it is strange.
- Blue, talking, flying shapeshifting kitten? Fine. Man whose hair suddenly changes colour? RUN AWAY! RUN AWAY!
Similar to the Saiyans above, Lalas race from To Love Ru are indistinguishable from humans apart from their tails. In a similar vein, there is Ren/Run whose only difference from humans is Gender Bendering. There are other examples of Human Aliens, but it is shown that there also exist Rubber Forehead Aliens and Plant Aliens, so at least the universe has some variety.
The S and Stars seasons of Sailor Moon brought so many Human Aliens (or at least aliens that were originally human in appearance) from across the galaxy to Tokyo that one could wonder if non-humanoid intelligent lifeforms really existed at all! Even the talking cats Luna and Artemis, who were aliens from the planet Mau in the manga, could assume human forms. (Rei's crows Phobos and Deimos were also revealed to be aliens who could take human form in the manga.) The filler arc villains Eiru and An from the start of the second season were also aliens who could assume human form, though the villains from the first season and the rest of the second season were originally from Earth.
- The Moon Kingdom inhabitants and the Senshi of the past could also count, since they're technically not from Earth. This also means Queen Nehelenia/Zirconia, the Big Bad from SuperS, would count, even though the rest of her minions are either from Earth originally (animals given human form, some girls from the rainforest given powers) or are dream-monsters (the Lemures).
The Arume in Blue Drop are human in every way, although their whole race consists of females only, leading to certain kinds of behavior.
- Some years later, sci-fi artist Nemo Ramjet revisited the concept as part of a series of paintings. His new "Dinosauroid" thankfully avoids this trope. (As a matter of fact, he looks sort of like a Fraggle...)
The Plants in Trigun look exactly like humans, all to various degrees. The ones used as power look semi-humanoid with wings and other assorted appendages, while Vash and Knives can easily pass for human.
The Juraians in Tenchi Muyo not only look human but have Japanese-sounding names.
- It's implied that Earth is actually one of Jurai Empire's peripheral planets and that there has been interaction in secret since times immemorial; according to the novels at least some of the Earth governments actually take orders from Jurai in the rare occasions that they bother to interfere. Emperor Azuza's second wife is apparently an Earthling from Feudal Japan whose life was technologically extended from normal human limits, and that's just the start of it.
- That explains Aeka, Sasami, and Yosho. Washu (and decendents Mihoshi and Ryoko), on the other hand, has less justification.
The nazi-inspired Gamilons from Space Battleship Yamato began as looking identical to humans in every sense of the word. However, the creators of the show retconned their design a few episodes into the show and gave them blue skin, blonde hair and black eyes. Why? Probably to distinguish them easily from the human cast.
- This is further developed when it's discovered that the Gamilons need radiation to survive, like how a human needs oxygen to breathe.
Lum and her family in Urusei Yatsura look almost exactly like humans, only with two small horns. However the series does feature other aliens in all shapes and sizes.
While no aliens other than the Anti-Spirals are actually shown, it's implied that Tengen Toppa Gurren Lagann follows this trope, based on the premise (used to justify Humongous Mecha) that the humanoid form is the best shape for channeling Spiral power.
The Time-Space Administration Bureau in Magical Girl Lyrical Nanoha covers multiple worlds but are all apparently human. One character comments on how somebody in her family history was from Earth when they were discussing "Unadministrated World #97".
In Houshin Engi, Taikoubou (later known as Fukki) is later revealed to be one of the "First Humans", which are actually an ancient race of aliens, although he looks exactly like a human.
Almost all throughout Dragon Ball, everyone just assumed Goku was an extraordinarily gifted human who just happened to have a monkey tail (and given the existence of anthropomorphic animals in Dragon Ball's world, this wasn't a far stretch). The Reveal that Goku is actually Kakarotto, a mercenary of a warrior race of aliens, doesn't come until the first few episodes of the sequel series.
The all-female Alpha Cygnans in Project A Ko.
In the series Inu Yasha, it's the demons who look human who are considered most powerful.
A similar notion extends to Yu Yu Hakusho, as quite nearly all of the show's most powerful demons appear human.
While not aliens, the main characters of Wolfs Rain spend a lot of time looking human, mainly as a form of camouflage, as they're supposed to be extinct.
Mahou Sensei Negima has an interesting take on this, in that the Magic World is in Another Dimension, that happens to be layered on top of Mars. Meaning that anyone from the magic world is technically an alien. Including Negi.
The Mu from RahXephon are entirely indistinguishable from humans save for their blue blood. Then there are some such as Ayato and Hiroko whose Mu-phase has yet to be activated, making them appear human in every way even to themselves.
Bakugan Battle Brawlers New Vestroia introduces an extradimensional race known as the Vestals. There's not much difference between humans and Vestals, aside from their eyes. Human eyes have distinct, black pupils, while the Vestal pupil is just a darker shade than their iris. Given this style of pupil can be the norm for humans in other shows, one might not notice the difference immediately.
The aliens from Niea_7 are human for all practical purposes, save for the shape of their ears and conspicuous antennae (for most of them) on top of their heads. Chada is somewhat of an exception, since he is plain ... weird.

Comic Books

In all Superman stories, Clark Kent and all other Kryptonians are visually indistinguishable from humans, despite massive biological differences (thus making this Older Than Television, although the fact that the Ancient Greeks also came up with the concept makes it Older Than Feudalism). All versions also show that Kryptonians can be attracted to humans, but the last episode of Lois And Clark has them finding out the two species are genetically incompatible (right before a foundling gets dropped on their doorstep). Science fiction great Larry Niven did address that issue in his hilarious essay Man of Steel, Woman of Kleenex. Of course, Superman Returns and some comics continuities have a half-Kryptonian.
- The Golden Age Superman had extraordinary muscle control, even allowing him a mild Shape Shifting ability for minor disguises. And in some Silver Age versions, Kryptonians were descendants of humans plucked from Earth by a more technologically advanced race. Some post-Crisis stories imply this as well.
  - To be fair, this has been addressed from time to time by different others: One graphic novel in particular, detailing Clark's life after leaving Smallville but before journeying to Metropolis, mentions that he has "unearthly blue eyes" which could never be mistaken for human; it's for this reason that he wears ultra-thick glasses - to dull the color, not just "mask" his face.
  - An old Superman/Flash crossover story has the duo facing a mysterious alien race that apparently seeded both Earth and Krypton with life, at around the same time, serving as a possible explanation for this trope.
  - Adding credence to the above point would be the fact that the Earth was originally meant to evolve a godlike race similar to the Kryptonians. They ended up as the weak, fragile primates called 'humans' only because another alien race messed with the pre-human gene pool.
  - Lampshaded in an issue of Starman where Jack Knight's journeys through space and time land him on Krypton before its destruction. He is promply arrested by the authorities, who suspect him of being a member of a Kryptonian rebel group. When Jack tries to argue that he's an alien visitor from planet Earth, his interrogator refuses to believe him, pointing out that he looks no different from any Kryptonian. Jack wonders whether God was feeling unoriginal.
- In The DCU's Legion Of Superheroes, most of the alien races are perfectly humanoid in appearance, although they possess various additional abilities. Post-Crisis, this was handwaved by having them be descendants of humans who were given superpowers in alien experiments. After they were freed by Lar Gand, they were placed in colonies around the galaxy to ensure Earth would have allies in the future.
- The oldest sapient life in The DCU, the Guardians of Oa, are basically human in form (the males have blue skin, that's about it.) The natives of Rann and Thanagar can even interbreed with humans. A few other humanish races exist, more if you count those whose only visible non-human trait is odd skin color.
- On Smallville, almost all the Phantom Zone aliens were human-looking (well, some were disembodied and possessed human bodies, but the rest were human-like). One had Hellish Pupils, that's about it. The shapeshifters Brainiac and Martian Manhunter stay human except on special occasion.
- The original reason for Superman's human appearance was that he was human - he was originally meant to be a super-highly-evolved person sent back in time from the far-distant future, when life on Earth was finally dying out. This backstory was changed before publication, but the rewrite had no impact on Superman's appearance or his powers.
  - That explains part of Red Son.
In the Marvel Universe, the Kree are divided into two races: the pink Kree, who look just like Caucasian humans, and the blue Kree, who look just like blue humans.
- Likewise, the Shi'ar are humanoid, with features such as feathers and eye markings just odd enough to be exotic. The Skrulls are slightly more alien, being egg-laying reptilians, but their females in their native forms appear as shapely Green Skinned Space Babes (who still have the ugly ridged chins).
  - Lampshaded in an issue of Excalibur where Shi'ar Cerise joins the team. She runs into Nightcrawler and the Technet (alien bounty hunters composed of all shapes and sizes) and demands to know which of them best resembles life on Earth. Nightcrawler points out that, ironically, she does.
  - The Skrulls' appearance varies widely depending on the artist. Kirby's original depiction had them as ugly little troll-like dudes with bug eyes. Later portrayals usually gave them human height and proportions, but occasionally an artist will harken back to their original appearance. Justified, really, since they're a race of shapeshifters who probably give as much thought to their height and proportions as we give to which shirt to wear in the morning.
- Also, the Celestials and Galactus are more-or-less humanoid, though details are obscured by their armor and they're freaking enormous. Since these are "gods" from before the Big Bang, who are known to have tampered with life throughout the universe, it's not too surprising that there are lots of humanoid races. This was lampshaded at times by John Byrne's claims that they only appear as the same species of any sentient being seeing them, but later revelations made this dubious.
- And then there are the Norse gods and Olympians.
  - While being extra terrestrial in the sense that they don't live on the surface of the planet, Marvel has been pretty consistent in saying that the various pantheons and mythical beings are "of Earth." The current Thor series makes frequent reference to the idea that humans and supernatural creatures, especially gods, exist in a spiritual symbiotic relationship.
In a similar manner to Superman, the Viltrumites of Invincible, of whom main character Mark is a human hybrid, are basically humans with superpowers, and, if they're male, mustaches. All of them. And that's it.
- Averted by literally every other race, especially the Flaxans, who had to study traces of Omniman's clothing to understand the properties of our dimension because they're so far removed.
The Wildstorm Comics 'Verse has Kherubim, super-powered humanlike immortals who can even interbreed with homo sapiens. It's eventually revealed that this is because Earth and other planets were seeded with devices designed to spread the Kherubim genome across the universe in a form of bloodless conquest. Not that they were averse to the bloody kind on occasion either, being a Warrior Race.
In the Sandman collection Endless Nights, Dream is courting a mortal woman named Killalla, whom he takes to a parliament of stars. Killalla looks just like a human being, but with blue skin. Justified in that while at the parliament, she encounters a young star named Sol, who admires her greatly and says that when his planets awake to life, he'd like for there to be a species that looks like her.
- Which, in a roundabout way, also explains the case of DC's Guardians, above, since Killalla is an inhabitant of prehistoric OA.
Bigsby Wolf and Snow White in the Vertigo series "Fables" have a litter of children who are either wolf-like, human or a combination of elements of both.

Film

All the alien races in Chronicles Of Riddick series. This gives the superficial illusion of Absent Aliens, but there are a few here and there revealed to be aliens. Such as the air elemental, who looks like a normal old lady, but can turn into mist as she chooses. And there's the protagonist, Riddick, who's Furyan.
- More of a shameless retcon from the first movie.
Practically all alien races in the Godzilla movies. (Although sometimes this is just a disguise for space gorillas or cockroaches.)
Thomas Jerome Newton in The Man Who Fell to Earth is actually a Rubber Forehead Alien, but appears human (as human as David Bowie is capable of looking, at least) throughout most of the film through the use of contact lenses and stage makeup. Without his cosmetics, his bright golden skin and eyes with vertical, ovular pupils would give him away. Biologically his people are essentially identical to humans, except for their long life spans (Newton remains the same age while other characters in the movie go from college age to their late 50s), and are extremely sensitive to X-rays, which blind them.
The squid-like Thermians in Galaxy Quest use appearance generators to look human. Somewhat justified: they based their entire society and technology on a human TV show, and they were trying to fit in with their human guests. Since they have no concept of deception, it isn't meant to let them pass for human or even to make the humans ease into the whole alien thing; it's just their version of Cosplay.
- Also, the Thermians built their Protector to look and control exactly like the one they saw on TV... which left them with a machine wholly incapable of being controleld by their actual bodies. They need human-shaped hands to use the ship!
Star Wars, of course, features Human Aliens alongside Serkis Folk. There's no sign of Earth, and what connections or differences exist between the totally-human-looking races of different worlds remains unknown. (One must wonder if there are other planets with, say, Wookiees that are completely unrelated to the ones of Chewie's homeworld of Kashyyk...)
- There are basically two contradictory explanations, one that humans evolved independently on Coruscant, and one that all humans are descended from escapees from the dystopic Earth of THX 1138 (another Lucas production). For example, Corellia was named for a human with the Italian name of Corellia. Neither explanation has been canonised so far.
- Knights Of The Old Republic, which is actually canon surprisingly enough (light side ending), implies that the human homeworld was actually Tatooine. The originals were the ancestors of the Sand People as well, who abandoned technology after a (technically) successful rebellion against the Rakatan that also led to the world being turned into a desert by orbital bombardment.
- In the Expanded Universe comics by Dark Horse, Indiana Jones finds the Millennium Falcon crashed on Earth and the bodies of Han Solo and Chewie after thousands of years of being stranded in a South American jungle.
The Lost Skeleton of Cadavra used this trope purposely with the "Marvans" as an affectionate spoof of low-budget sci-fi horror movies from the 50s.
Lattis:It's interesting how different people from different planets differ.
Justified or Handwaved in the remake of The Day the Earth Stood Still, where Klaatu arrives on earth encased in something like an engineered placenta-suit, inside which he grows himself a humanlike body resembling Keanu Reeves. He explains that his true form "would only frighten you."
- Actually, the reason he assumed that form is because only an organism that originated on Earth could survive in its envoriment without some sort of assistance. The above explanation came as an answer to a human who was curious about his original body.
The upcoming Disney movie Race To Witch Mountain. The aliens look exactly like humans... but then there's the superpowers.
- When ~~The Rock~~Dwayne Johnson's character points this out, they respond with "What's an alien supposed to look like?"
Dr. Frank N Furter, Riff Raff, Magenta, and the other Transylvanians look like normal human beings. Considering that the film is an Affectionate Parody of old B-Movie science fiction films, it's no surprise.
It's strongly implied in Outlander that Kainan's people are related to humans, as his computer describes Earth as an "abandoned seed colony".
District 9 notable averts this by having the aliens look like bipedal prawns, hence why they're called that. What really works in its favor is that it has actually alien aliens rather than some selected human ethnicity given some cosmetic changes and called aliens.

Literature

All visual incarnations of The Hitchhiker's Guide To The Galaxy, despite the fact that its other alien races are incredibly diverse (pan-dimensional mice, superintelligent shades of the color blue, etc). Arguably, this was deliberate, as the idea that "outer space is just like Earth only a little weirder" is one of Hitchhiker's main jokes.
Robert Rankin shamelessly lampshades this in one of his stories (Armageddon, the Musical I think) where it is advanced as proof that there is a God who designs dominant species in his own image. "As any science fiction fan knows, the basic human shape, Head at the top, two feet at the bottom, wedding tackle about halfway down, is the standard for intelligent life the universe over. They often speak good English with a noticeable American accent, too. Facts that should serve up friend Atheist with a workload of eggs, faces for the use of."
In one Discworld book (though it was referring to gods, the spirit's the same), it's mentioned that if you ask someone to come up with an alien-looking being, it would basically be a man in an animal mask.
Edgar Rice Burroughs did this all over the place starting back in 1912 with A Princess of Mars. Everybody on Mars except the Green men looked human, but hotter. The earth born hero John Carter and his Martian Princess wife have two kids, despite massive biological differences including Martians being oviparous. This doesn't even begin to cover some of the wild biology that shows up in the Land that Time Forgot stories.
The Takisians of the Wild Cards series. In fact, that's what leads to the entire plot of the series; the Takisians note how biologically similar they are to humans, believe they must be the descendants of a "lost colony," and drop the wild card virus on Earth to test out its purpose as a biological weapon.
The various biological species of The Culture are mostly human-looking, although they have various additional internal glands and bits. Given the degree of casual genetic modification in the universe though, it's anyone's guess as to whether they were all always like that.
- In The Use of Weapons, Shias Engin asks Zakalwe "I know that all the outworlders aren't humanoid, but a lot are. How come?". Zakalwe replies jokingly that it is the universe's way of getting rid of alcohol.
- Some of them are human, a result of The Culture grabbing some of them to spread out across the universe.
In Ursula K. LeGuin's series the Hainish Cycle, this is because all the humanoid races are from planets colonized by the titular Hainish. Including Earth humans. Despite a common ancestry, they don't all look like us. The Cetians are hairer, for example, and the Athsheans are green (fairy green, not Martian green) and diminutive.
In James Patterson's The Dangerous Days of Daniel X, the aliens on Daniel's home world, Alpar Nok, look exactly like humans. The planet even looks like Earth.
In the Perry Rhodan universe, the ancestors of the most prominent 'human alien' races of our galaxy actually came from Earth. (Extra irony points for one of those species later coming back and, quite unaware, claiming 'Larsaf III' as a colony of their own for a brief time.) Humanoid life in general seems to have some common ancestors in the distant cosmic past, and can also be partially justified by the fact that Sufficiently Advanced Aliens have been known to meddle in the evolution business as well.
Justified in C.S. Lewis's Space Trilogy (see page quote above), whose premise is that The Bible is true: since the Son of God became a human, any intelligent beings created after Jesus' birth will also have human form.
- Jadis in the Narnia series may also qualify, as God in this series has created nearly identical animals on other worlds. This also results in such things as Bear Aliens and Mouse Aliens. On the other hand, Jadis may be descended from Transplanted Humans, like the Narnians.

Live Action TV

Doctor Who did this more times than can be counted. The most famous examples are, of course, the Doctor himself and the other Time Lords. Their most noticeable physiological differences (two hearts, 60-degree Fahrenheit body temperature, a far more complex brain structure, a respiratory bypass system, "symbiotic nuclei" in their cellular structure, and whatever organs or systems are responsible for their ability to regenerate) were effectively invisible to the television viewer.
- The Expanded Universe did a Lampshade Hanging by having a racist founder of Time Lord society, who thought that the Time Lord form was supreme to any other, go around the universe and infect species with a virus that would cause them to evolve into humanoid forms.
- Earlier, the Expanded Universe lore had come up with a completely different Lampshade Hanging, also involving the Time Lords. The Time Lords evolved first out of all sentient species. Therefore, the morphic resonance of Time Lord-ness propagated throughout the universe.
- Yet another lampshade was hung in the Easter 2009 special Planet of the Dead:
Christina: "You look human."
Doctor: "You look Time Lord.''
- Thals and Kaleds look like humans. The Stolen Earth reveals that they have fewer ribs than humans and Bizarre Alien Biology, though.
Star Trek The Original Series had several, and it was rather strange when Spock was the only crew member who had to disguise himself on an alien planet. (It was even stranger when Kirk's Beleaguered Childhood Friend was able to make himself dictator of an alien planet without any of the aliens noticing something odd about him.) In fact, aliens are Human Aliens more often than not, probably for budgetary reasons.
- Star Trek The Next Generation attempted to provide an explanation for the prominence of humanoid species (both Human Aliens and Rubber Forehead Aliens) in the universe by revealing that there was a common ancestor race that "seeded" the galaxy with its basic genetic material. They switched to exclusively using Rubber Forehead Aliens rather than Human Aliens after the first few seasons (excluding Guinan's people, the El-Aurians and Councelor Troi's, the Betazoids).
  - Betazoids actually do have one distinguishing feature from humans - their irises are completely black. A shame too, Marina Sirtis has gorgeous green eyes, but you'd never know it from the show.
  - The Trill as they appear in DS9 , are also closer to this than Rubber Forehead Aliens, at least on the surface; their main distinguishing facial feature are their spots.
- Star Trek Voyager had a few Human Aliens in its first season, too, mainly wearing strange and colourful national dress.
- At least Star Trek The Original Series had a few attempts at using body paint for doing alien skin colours. Voyager had an absurd number of aliens who were virtually indistinguishable from humans, even in later seasons when they had a high budget.
  - In fairness to Voyager, they did require a new alien species almost every week as they were travelling constantly. This would require a certain amount of cost-cutting — remember the fuss when the Kazon kept reappearing for two seasons?
  - That had more to do with the fact that they never really seemed to be a threat. It's one thing to have a recurring villain that the heroes often encounter, but when they think drawing a line on the floor and telling prisoners not to cross it is good enough security not to post a guard it's really hard to take them seriously.
- An early Star Trek Enterprise episode dealt with the bizarre culture of humans acting like aliens (much like the Stargate examples below), where it's justified as the current population is the children and grandchildren of the human settlers of the first Earth colony.
- Actually, Aliens and Humans are genetically close enough that they can interbreed, as Spock himself is an example of.
Stargate SG-1 and Stargate Atlantis partly subvert this trope by setting up the premise that the Milky Way, Pegasus, and Ori galaxies are filled with actual human beings due to being kidnapped from Earth and seeded on different planets by various Sufficiently Advanced Aliens. Of course, this doesn't explain why every human culture they encounter on these shows speaks English. See Aliens Speaking English for some thoughts on the matter.
- Note that this is pretty hilarious considering that almost the entire plot of the original Stargate movie consisted of Daniel Jackson trying to figure out the elaborate language of the planet they gated to.
  - Not any more elaborate than any other human language; it started out as Ancient Egyptian and then drifted for several thousand years (and should have changed vastly in that time—consider that, 5000 years ago, the language that was the remote ancestor of Latin hadn't really developed yet— but having undying gods around does tend to freeze things in place).
- It should also be noted that the humans are related to the ancients in some way, which explains the similar appearance. Likewise the Jaffa were genetically-altered humans. So while all three races look the same (for the most part, Jaffas do have a visible pouch on their stomach) it's because they're all related in the first place. Of course, Humans still manage to get around being, apparently, the most populous race in the Milky Way, Pegasus and Ori galaxies.
  - The humans in Pegasus and the Ori galaxy were seeded by the Ancients through genetic engineering, and are not directly descended from them, despite the use of the term "ancestors" in Pegasus. The humans on Earth presumably came about the same way. Humans were not seeded on any other Milky Way planet, the Goa'uld brought them to those worlds from Earth.
  - A Goa'Uld named Hathor actually turns Jack O'neill INTO a Jaffa in one episode, although it only lasts a few minutes, as he's placed in a sarcophagus and returned to normal. (Is there a trope for this?) jaffa were humans altered by the Goa'Uld queens and a hand device that altered their bodies.
  - Yes, it's called Discontinuity.
- Also, while the hyper-advanced Asgard appear to be your typical Greys, one episode does show that their ancestors were, in fact, not unlike humans in appearance (except for the gray skin). Their current condition was caused by thousands of years of Cloning. This suggests that they may also share a common ancestor with the humans/Ancients.
The three alien kids from Roswell who looked human, but prettier. It's gradually established that they are actually traditional Roswell greys in human form. The thing is, they assumed these forms before exploring outside their crashed spaceship as children. The reason they knew to do so was later HandWaved by explaining they are Half Human Hybrids. Whew!
On Farscape, the Sebaceans. Same thing happened to them as the aliens on Stargate. As a bonus, this explains their absolutely absurd vulnerability to heat (as well as their numerous superiorities to humans, such as keen eyesight and ability to breed with humans); it was engineered into them by their abductors as a control mechanism. Considering that, in real biology, one of the things that makes humans special is our ability to withstand overheating, there's no way that could have happened naturally. Though even before the reveal this was something of a subversion, as the show is noted for its many decidedly non-human looking aliens, which were Muppets at least as often as actors in prosthetics, so the fact that humans and Sebaceans look exactly alike is considered quite weird. Not to mention, since the human John is the alien far from home, everyone they meet natually assumes he's a Sebacean, which often plays right into the heroes' hands.
- For that matter the physiology of the Luxans made no sense either, so, this editor took the heat vulnerability in step and just kept going.
  - Or the Delvians. Or...
Mork, of course. He was even able to have a kid with Mindy (although he was the one who laid the egg, and the kid was middle-aged Jonathan Winters.)
Power Rangers really abuses this trope, invoking it for more or less anyone who isn't a rubber-forehead-alien or a robot-ish thingy. They even call themselves humans, for the most part.
"What, you think Earth is the only place humans come from?" -Andros in his first appearance
The Centauri from Babylon 5 look human, except for their hairstyles, double hearts (and lack of major blood vessels in the wrists), and tentacle-like genitalia. Possibly justified in that Vorlons had tampered with the evolution of younger races on numerous occasions.
- This was lampshaded in the first episode, where it is revealed that, after encountering humans for the first time, the sneaky Centauri claimed that their physical similarity was due to Earth being a long-forgotten Centauri colony. Human scientists, no doubt keeping the fossil record in mind, got hold of some Centauri DNA and disproved this claim. The Centauri saved face by claiming "clerical error" had mislabelled Earth as a lost colony. Internally they are completely different.
The aliens on 3rd Rock From The Sun mention a few times that they've taken on human form and describe their natural form as being "purple tubes". It's never quite clear whether they're using stolen bodies from real humans or if they somehow created their human bodies from scratch.
- The first words spoken by High Commander Dick Solomon on arriving on Earth are "Everyone fully formed?", which would indicate the latter.
- Also, they make jokes about having leftover parts in storage, and at one point bring down a pet from their ship and put it in a human body.
Arguably the Cylons from the new Battlestar Galactica. But this instance is justified. "The Cylons were created by Man..." And they WANTED to become like humans. For, among other reasons, sex and having children. Also, Humans apparently evolved independently on both Kobol and Earth. Kobol first.
- Not necessarily. We have good reason to believe that Sufficiently Advanced Aliens have been screwing around with humans for some time. It's not impossible that the people of Kobol were originally taken from Earth. After all, the only records of Kobollian civilisation are ancient religious texts - the Colonials may believe that they evolved on Kobol, but they don't actually know that.
- Doesn't matter. In terms of us, they are humanAliens that finally found OUR Earth, but since we are their descendents, aren't we also Human Alien?
Odyssey 5 had Synthetics, which were human bodies created by artificial intelligences. At one stage the team consult a sci-fi writer, pretending they're looking for help with a sci-fi novel. The writer complains how cliched the idea of Synthetics is: "It's just a cheap tool TV shows use to save on special effects!"
A nice Hand Wave comes from the TV show Something Is Out There. "God created human beings in his image, right? How many images do you think he has?"

Video Games

Super Robot Wars: Original Generation reveals that all the Human Aliens are actually humans, who left Earth long ago voluntarily. The Mysterious Lovecraftian Aliens refer to Earth as the "Land of Beginning", where sentient life first evolved.
Galactic Civilizations II has a race called the Altarians, who are essentially Humans With Psychic Powers. The Altarians even call the Terrans their "lesser cousins." It's implied in the backstory, however, that the two races might have a common origin.
Toejam And Earl 2: Panic on Funkitron plays with this by having the hero's planes being invaded by humans. Hilarity Ensues.
Star Control II is mostly pretty good about making its aliens different from humans, though there are still a suspiciously large number of bipeds with heads on the top. However, one species, the Syreen, are your typical blue-skinned space babes - and they comment on the perplexing similarity between their species (the big difference being matriarchal rather than patriarchal). They're so close, in fact, that they're apparently sexually compatible, capable of producing fertile offspring. It is implied in the game's rich backstory, however, that it's because a certain other alien species transplanted some ancient Syreen to Earth as part of an extremely long-term experiment.
The Lunarians in Touhou are basically this. But then again, they might be merely ascended humans after all.
Similarly, the Lunarians in Final Fantasy IV don't look too different from humans other than slightly different skin tones and hair colors. They can even interbreed with humans and the two major characters are Half-Lunarian.
The vast majority of the alien races in Star Ocean are human or Petting Zoo People. This may be justified by the third game's Shocking Swerve if the player thinks about it.
The Jak And Daxter series takes place A Long Time Ago In A Galaxy Far Far Away, and their equivalent of humans have long Pointy Ears, but for all intents and purposes, they are human, and are even called "humans" in-game.

Western Animation

Ben10 plays with this trope a lot. For starters, most of his aliens are of a fairly human shape, so even when he transforms, he doesn't have to deal with totally Bizarre Alien Biology (though even Plant Aliens don't give him any trouble figuring out - apparently the Omnitrix downloads a detailed knowledge of the new form's abilities into his brain that Ben can call up subconsciously when necessary). Then in the sequel, Alan is a Pyronite crossbreed who looks human except for when he's using his powers, and it's revealed that Gwen is a Half Human Hybrid and gets her powers from her alien grandmother (the logical extension is, of course, that anyone without an Omnitrix strapped to their wrist who has powers is an alien or part-alien. The fans have had fun with this).

Aversions and subversions

The First Breed from His Majesty's Starship look nothing like humans.
- Although books are naturally far less vulnerable to this trope than Live Action TV, given that it takes significantly less effort to write a character as a "20-foot arachnid" than it does to act said spider.
Prot in K-Pax explains this by saying that it is the most energy efficient form to take on Earth. Of course, he may or may not be an alien.
- In the earlier film which might have inspired the novel, an Argentinian production called Hombre Mirando al Sudeste (Man Looking Southeast), Rantes explains to the doctor that though they came in a ship, he and the others are actually physical projections from a distant, doomed future on another planet, and that they naturally adapt to whatever the observer expects to see. Of course, he may not be an alien, either—though he does have Psychic Powers, and his equally-alien (?) female friend does leak blue liquid from her mouth when excited, and then again, he also claims to be The Messiah...yeah, it's one hell of a Mind Screw.
Subverted in Monster Buster Club; Cathy seems like a Human Alien at first glance... but various lines indicate that this is just a human disguise like we see on other aliens in the series, and her true form hews closer to the Starfish Aliens trope.
Both the Transformers & the Brave Series have a weird variation on this, wherein there are several planets besides Cybertron/whatever planet the heroes come from that are inhabited by intelligent Transforming Mecha. Sometimes explained as being colonies of the main characters' race, sometimes not. While it may be reasonable to assume that a sufficiently advanced civilization would discard their weak organic bodies for more durable mechanical ones, the whole transforming thing is pushing it. The weirdest example being the Japanese Beast Wars II series, where there is a planet of highly evolved Funny Animal-like aliens who have developed to the point of Trans-funnyanimalism, where they have upgraded themselves with cybernetics. This allows them to turn into humanoid robot forms that look uncannily like the Maximals & Predacons, despite having no prior contact with them, for no apparent reason other than Rule Of Cool.

Anime

NeonGenesisEvangelion, oddly enough several of the Angels are roughly humanoid, others are more... interesting. Notably, the two most powerful ones are basically cloned Half Human Hybrids.

Literature

Averted in the novel Transformers: Ghosts of Yesterday (a prequel to the film), where Starscream claims that any sufficiently advanced race would naturally build machines that were similar to Cybertronians, as the Decepticons believe that they are the most perfect lifeforms in the galaxy. However, he also may have been simply trying to explain away the fact that the human spaceship Ghost 1 seemed to be built using Cybertronian technology (i.e. that Megatron, the Decepticons' true leader, has been found).
Conspicuously and consciously avoided in Wayne D. Barlowe's illustrated sci-fi novel Expedition. Barlowe, a noted fantastic fiction illustrator who darn well knows his biology, openly despises this trope and so he invented an alien race who is very like humankind in their attitude and culture - but they look a bit like a cross between a hot air balloon and an airborn octopus.
In Larry Niven's Ringworld series, there are various humanoid races who all turn out to be descended from the same race of Precursors who are the ancestors of Earth humans.
The Martians and Venusians of S.M. Stirling's The Lords Of Creation novels look human because they are (more or less); the eponymous beings, in prehistoric times, Terraformed Mars and Venus and seeded them with Earth life (repeating the process several times, so that on Venus you have humans sharing the planet with dinosaurs and mammalian megafauna).
The aliens in Robert Zubrin's The Holy Land consider themselves the humans, and the Earthlings merely 'proto-humans'. Given their superior senses, telepathic ability, superior physiques, and superlative hygiene, they're probably right. However, they themselves originated on Earth, about twenty thousand years ago.

Live Action TV

Babylon 5 had a strange inversion. The Vorlons are so alien looking that for the first two seasons we don't know how much of them is clothing and how much is their real body. Their true form appears to some kind of energy being, but every species perceives a Vorlon to look like their species version of an angel — it is suggested that this is the result of the ancient Vorlons having not only genetically tweaked the other species, but also appeared to them as angels at appropriate times in their respective development, creating the basis for the legends.
Firefly pointedly avoids this trope. If the people on the next planet over look human, that's because they are. Yes, even the Reavers.
TNG had a weird variation once: apparently, it's not just humans that have doubles. "Who Watches the Watchers?" features a alien species that are physically identical to Vulcans (or at least Romulans, who are basically Vulcans with a ridge to make them distinct from their Federation cousins) without being a descendant.
Subverted in an episode of The Twilight Zone in which astronauts are surprised to find Mars inhabited by human beings.

Radio

Parodied in the Captain Kremmen radio spoof, when Kremmen first encounters the Thargoids.
"Except for their large transparent heads, three lips and sixteen nostrils, they looked just like you or I!"

Tabletop Games

Subverted in Cthulhu Tech. The Nazzadi look like Rubber Forehead Aliens, but that is because they are actually genetically engineered from humans by the very alien Migou.
Traveller Role Playing Game both uses and subverts this; there are humans and humanoids spread by mysterious Precursors, and there are Starfish Aliens, some of them very alien.

Video Games

Dead Space has an ironic subversion, since all the Necromorphs are made from human corpses and several of them look pretty damn close to a plain old human.
Mass Effect has many races that are distinctly non-human. The Elcor look like smaller elephants with 4 big legs and no arms and the Hanar look like floating jellyfish. How species without any prehensile limbs can manage to create technologically advanced civilizations with faster-than-light travel is a puzzle for this Troper.

Web Comics

Alien Dice has numerous examples of aliens who look similar to humans but with subtle differences, such as exotic Hair Colors or Cute Little Fangs. It also has a rather interesting subversion when it is revealed that the reason that the blueskinned Rishan look human is because they are human, having been created using genetic material taken from Earth humans generations ago.
El Goonish Shive. Aliens and magical beings get around by wearing T-shirts that say "Human" or some such. (One person notices that his coworker is an alien. Her denying it is enough to convince the others, and she and this coworker wind up sending silly notes back and forth to each other about it.) Of course, Uryuoms being natural shapeshifters and the creators of Transformation Ray technology, they could hide by simply becoming human. Of course, that wouldn't be funny.
- Two of them hire Ted (seen in a flashback) to design human forms for them, and provide the technology for it - apparently there are legal/political/religious reasons why they can't do it themselves, rather than an inability to do it themselves. Also, once they've been raygunned into humans, they can (implied) shift back and forth freely.
- It gets better. Uryuoms don't consider themselves actual aliens—as one of the pair who hired Tedd said, he's natural-born American! Hence the above argument—the other characters knew she wasn't human, but she's not alien. Wonderful thing, jus soli, eh?

Western Animation

Deeply subverted in Invader Zim. Zim is small and green, with antennae, but everyone else is so oblivious that no one notices.
- But he has his human disguise! He puts in his contacts and wears a wig - INGENIOUS!!! evidence◊
Captain Crandall of Teamo Supremo claims to be from another planet, despite the fact that he looks too much like his "Earth-mom" to possibly not be her child.