Animals by neisbeisOne of the interesting things about fictional aliens is that they’re almost never completely alien. We have no real idea what extra-terrestrials would look like, and it’s nigh impossible to imagine an entirely new species unlike anything we’ve ever seen. As such, we usually fall back on earthly species for inspiration, combining known elements to create strange new creatures. And we certainly have some bizarre real animals to choose from.

Last year I wrote about our penchant for basing aliens on cephalopods, but octopuses, cuttlefish and squids aren’t the only creatures that inspire us, so I thought I’d take a step back and look at a broader range of favourite sources:


Self-centred as it may be, it’s no surprise we often imagine aliens are similar to ourselves. An upright vertebrate with two legs, one head and two eyes is easier to empathise with. Making up a human actor is also easier than mechanically animating or computer generating a creature with an entirely different shape, size and pattern of movement – undoubtedly the reason why Star Trek has a lot of humanoid aliens.

Na'viEven films that rely heavily on CGI, like Avatar, create aliens whose movements and expressions are based on those of human actors, though the empathy factor is also at work in that example. James Cameron even mentions how he aimed to cross the uncanny valley to make the Na’vi human enough to be attractive. (Also, who wants to watch a romance between a human and a tentacled cephalopod?)

Some science fiction novels, such as The Left Hand of Darkness and Hyperion, refer to humanoid aliens because they originally were humans. In both, the universe has been colonised by humans who have diverged genetically after many years of separation.


I’ve previously gone into more detail about why we love to base aliens on our cephalopod friends. It’s not just the creepy appearance of an octopus or a squid, but their dexterity, intelligence, skills and genetic difference that make them prime alien-inspiration fodder.


Sometimes it’s just the tentacles that get borrowed, as with H. G. Wells martians in War of the Worlds, but the inspiration doesn’t stop there. The aliens in Independence Day and Arrival have even more in common with squids and octopuses, borrowing everything from their ability to squirt ink, to their slimy skin and triangular “heads”. Even the aliens in The Simpsons are just talking, green, fanged octopuses.

A monster by mingrutu


Arthropods come in a close second to cephalopods on the alien front, and many fictional extra-terrestrials combine aspects of the two. Perhaps it’s not only the creepy exoskeletons and many legs of insects, arachnids and crustaceans that appeal, but the nightmarish prospect that during one period in earth’s history, these creatures used to be much larger than they are now.

The most notable arthropod aliens that come to mind are the ill-treated and derogatorily named “prawns” in District 9, the cockroach-like antagonist in Men in Black, and the “buggers” in Ender’s Game. The face-huggers in the Alien films also have a very spider-like form and a parasitic function.


Reptiles make an appearance too, and it’s not just their frightening qualities and unusual skin, but also their history that makes them candidates. As we dig up the bones of long-extinct dinosaurs, it’s not hard to imagine these creatures on other worlds, or to imagine a version of history where they survived and further evolved into intelligent “dinosauroids”.


The Xenomorph Queen in Alien, while bug-like in some ways, is very reptilian in shape and feature, and particularly reminiscent of predatory theropod dinosaurs.

Humanoid reptilians are particularly popular in sci-fi TV Shows. Think the Visitors in V, the Gorn in Star Trek and the Draconians and Ice Warriors in Doctor Who, the Trandoshans in Star Wars and the Unas in Star Gate. To be fair, all these shows featured so many aliens that they may have used every animal in the book. Doctor Who alone boasts a huge selection.


Experiment 13 by AledinAmphibians, and in particular frogs, are used for their smooth, moist, and sometimes luridly colourful skin, as well as their overly large eyes, long tongues and four-fingered feet with bulbous sticky fingertips.

The classic little green men from UFO sightings and pop culture (figures with thin humanoid bodies, bulbous heads, large eyes and smooth skin) owe perhaps as much to amphibians as they do to arthropods and cephalopods. Even Spielberg’s E.T. has glowing bulbous finger-ends a little reminiscent of the finger pads of frogs.


The above might be the most popular, but they aren’t the only types of creatures we base aliens on – the bear-like furry Wookies in Star Wars and the giant sandworms in Dune are evidence of that. Sometimes storytellers and artists also push the boundaries further, creating aliens that are so unusual they don’t quite look like anything we’ve got on earth, or that are a mash up of so many different features it’s harder to tell what inspired them.

Dune by Frank Herbert (detail)Heinlein’s Martians in Stranger in a Strange Land start out as ball-shaped “bouncers”, then become three-legged adults, and eventually die and become “old ones”, which also exist in the spiritual realm. The aliens in the film Edge of Tomorrow have a dog-like four-legged shape, though they do have some tentacle-ish action going on, and move in a rapid, smoky, unearthly kind of way, as well as lighting up like machines.

Illustrators and artists also invent intriguing new creatures. For example, sci-fi concept artist Alex Ries combines his passions for science fiction, zoology and biology to create detailed illustrations of alien species and worlds. Notable are his intelligent hexapodal Birrin, which are often depicted using their technology to explore the more hostile environments of their world (e.g. trudging through frigid winter landscapes or deep-sea diving), as well as outer space.

Birrin by Alex Ries

Of course, opinions on what aliens would actually look like differ greatly, and discussions on the topic inevitably involve deciding what the universal rules or prerequisites for life are (for example, must all life be symmetrical?). Part of the fun of all this is that we have no idea what life forms different planetary conditions might give rise to. This can be frustrating for the many of us who would love to know what’s really out there, but it does leave the field open for creators to let their imaginations run wild.

Title image by neisbeis.


By Nicola Alter

grew up in regional Australia and now lives in Germany, where she’s enjoying all the castles and cobbled streets the Black Forest has to offer. She has a BFA in Film and Television and an MPhil in Creative Writing, and has worked as a production assistant, a writing course tutor and a project manager at a foreign language institute. Now she writes full-time and spends the rest of her time learning languages, travelling, and devouring fantasy and science fiction of all kinds. You can follow her on Twitter @NicolaAlter or visit her blog:

One thought on “The Creatures We Base Aliens On”
  1. There are very good reasons to assume that creatures from an Earth-like planet would be very similar to Earth creatures. Because all our animals are evolved to be adapted for an Earth-like environment. Bones, muscles, legs, lung, heart, stomach, eyes, ears, brains are probably something we’d find in all land creatures larger than insects. If they come from Earth-like planets. That still leaves a huge range of possible shapes and arrangements of these things (evolution does not push for perfection, only for good enough to not go extinct) and of course doesn’t even touch on creatures evolved in very different environments. (Though some universal laws of chemistry strongly indicate that carbon and water based life is the most probable, as these require elements that are extremely common, have countless possible combinations, and mix and react very easily. To get life out of raw elements, you need a lot of chemical processes happening by random chance. Starting with things as common as carbon and water, and with as many possible proceses increases those random chances by a lot.)

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