Flint: You mean flamingos!
Brent: There's a bunch of shrimp!
Manny: They look like chimpanzees.
When it comes to Worldbuilding, writers often want to populate their world with a fantastic fauna different from our own. However, at the same time they want this fauna to be somewhat believable and/or familiar to the viewers. One way to achieve this is to make some of the fantasy species the exact counterparts of a real-world animal. Thus, we end up with things like giant insects flocking like pigeons, giant reptiles hunting in packs and howling like wolves, or tentacled creatures swinging from trees like monkeys. In a sense, each species acts like an Expy or a Suspiciously Similar Substitute of a different species.
The trope has two main variants. In one version, a number of fantasy/alien/prehistoric species are presented as counterparts to mundane, modern species. In the other version, the animals are mundane species, but clearly fill the role of other, more familiar species — for example, an underwater setting where fish and other sea creatures act like mammals and birds, a Mouse World where insects and other invertebrates are counterparts to larger animals, or a World of Mammals where there are other classes of animals replacing non-sapient mammals. A World of Funny Animals setting can use this trope to avoid Furry Confusion — if certain species are anthropomorphised, their original niche is filled in by a different species.
To qualify for this trope, it is not a requirement for every species in the setting to have a real-world counterpart. For example, the setting can have giant monsters or magical beasts which, naturally, don't have any real-life equivalent. Regular, mundane animals can also appear in the setting (even if they might have different names). As long as there is at least one species that plays the role of an obviously different real-life species, it counts - but of course, the more such species there are, the better. If the only fantastic species like this is the counterpart to a dog or a horse, add the example to the respective subtropes instead.
This phenomenon, to an extent, exists in Real Life and is called convergent evolution. It's a well-recorded phenomenon that in different parts of the world and/or in different time periods, species largely unrelated to each other but filling the same ecological role (niche) will evolve similar anatomical and behavioral traits, in response to similar pressures. However, these similarities will usually be superficial. But fiction likes to exaggerate this, with the fantastic species acting virtually identical to their real-world counterpart. They might even have surprisingly mundane names.
Common in fantasy and science fiction as well as in Speculative Biology. Specific variants include All Animals Are Dogs, All Flyers Are Birds, Seahorse Steed, and Horse of a Different Color. When these are counterparts to pest animals specifically, this will likely overlap with Fantastic Vermin. If the animals are even named after their real-world counterparts, that's Call a Smeerp a "Rabbit". Compare Animalistic Abomination, where an Eldritch Abomination shows resemblance to a mundane animal; Call a Rabbit a "Smeerp", where the fantastic species is identical to the mundane species apart from its name and small cosmetic differences; and Informed Species, when an animal is intended to be a mundane species but doesn't look much like it. More often than not, these will be Mix-and-Match Critters. Might be subject to Binomium ridiculus if the writer wants to be scientific about it. Also compare Fantasy Counterpart Culture and Fantasy Counterpart Religion, where fictional cultures and religions replace real-life ones in a similar manner.
- Prehistoric Park Reimagined: Many of the prehistoric animals take on behaviors, environmental roles, and niches similar to many modern day animals, with several larger herbivorous dinosaurs taking on roles similar to elephants and rhinos, dromaeosaurs and other raptors behaving similarly to jackals and wolves, the smilodon populator behaving a lot like lions, some prehistoric carnivorous fish like Dunkleosteus and Onychodus behaving similarly to sharks and eels, and even temnospondyls and pelycosaurs behaving similarly to crocodilians and monitor lizards.
- A Bug's Life: The Ant Queen keeps an aphid as a lapdog, while P.T. Flea uses millipedes as oxen to pull his circus train.
- Cars: In a world of living vehicles, farming machines take place of cattle — tractors act like cows, gently grazing on wheat fields and tipping over when someone honks at them, and Frank the combine harvester acts like an aggressive bull, attacking cars who enter his field. There are also tiny VW Beetles that take the place of insects, and the credits use submarines in place of whales and sea monsters shown on old maps.
- Cloudy with a Chance of Meatballs 2: The characters discover that the FLDSMDFR has created an entire ecosystem of sentient food items ("foodimals") that often resemble real-world creatures, mostly with Punny Names. There are flamingo-like mangos ("flamangos"), chimpanzee-like shrimps ("shrimpanzees"), elephant-like watermelons ("watermelophants"), hippopotamus-like potatoes ("hippotatomuses") and so forth.
- The opening narration of How to Train Your Dragon refers to dragons as the pests of the island Berk, comparing them to mice or mosquitoes. In contrast, the ending narration refers to them as the pets of Berk, comparing them to ponies or parrots.
- In the sequels, shorts, and series, dragons are often used in similar ways to livestock animals, such as dragon racing.
- Luca: The sea monsters herd goatfish that bleat like actual goats, and Luca even uses a shepherd's crook to handle them. Luca's father also raises crabs that he treats like show dogs.
- Onward: In this Urban Fantasy story, dragons are the equivalent of dogs, whereas unicorns, out of all things, are garbage-eating, hissing pests in the vein of raccoons. There is also a reference to a dish called "griffin nuggets", indicating that griffins are the equivalent of chickens.
- Rango takes place in a Mouse World inhabited by Funny Animals, but some species, rather than being anthropomorphic, take the place of domestic animals. Roadrunners are the counterparts to horses, and javelinas (small wild pigs) are draft beasts filling the role of oxen. Then it becomes weirder when one background character, a blacksmith, is an anthropomorphic javelina...
- Avatar: Pandora's wildlife has a number of species that have a clear counterpart on Earth. The Na'vi are humans, of course, but the thanator is essentially a giant panther, the titanothere is a rhinoceros, the prolemuris are monkeys, the direhorses are horses, etc. The extended cut also features sturmbeest, which for all intents and purposes are buffalo (even being hunted by the Na'vi on horseback to further their resemblance to Native American hunters).
- The Dark Crystal: Some of Thra's native fauna fits the bill. The long-legged landstriders are the equivalent of horses, the round fuzzy fizzgigs are barking pets similar to dogs, and the nerbies are large, tame animals farmed for their meat, skin and milk similarly to cows. The armaligs can be seen as the equivalents of armadillos, but they have a very unusual role as the wheels of the Skeksis' carriages.
- Star Wars has quite a few examples, such as banthas (shaggy yak-like creatures) and dewbacks (reptilian dinosaur-like beasts) being the camel-analogues on the desert planet of Tatooine, or the wampa (a yeti-like furry beast) being the equivalent of a polar bear on the ice planet Hoth. The Last Jedi also has fathiers, large creatures resembling a cross of llama and jackrabbit that are used as gambling racehorses on the casino-like planet Finn and Rose visit.
- The Brightest Shadow: Monstrous aurochs — the wild ancestors of domestic cows — fill the role of cattle, cockatrices are raised like chickens, and bicorns are similar to goats.
- In Harry Potter, fairies behave like insects. Garden gnomes are small garden vermin similar to gophers and moles. In some wizarding households, kneazles take the place of house cats, though just as many households have regular cats. And most notably, owls replace pigeons as messenger birds in the wizarding world.
- Dougal Dixon's Speculative Biology books love this.
- After Man: A Zoology of the Future has so many examples that it has its own page, as the book makes heavy use of illustrative examples to display convergent evolution. In particular, rats have taken over most of the niches left by now-extinct carnivores and developed into a variety of marten-, wolf-, bear- and seal-like forms, while the rabbucks — long-legged, running rabbit descendants — include species equivalent to deer, camels, antelopes, zebras, giraffes and even warthogs.
- Man After Man: An Anthropology of the Future has the descendants of humans taking on these niches. There are grazing ape-like humans, sabertoothed carnivorous humans, manatee-like aquatic humans and small parasitic humans to name a few, with tons of Uncanny Valley to boot. The original set of examples is explicitly invoked in-universe — after most of Earth's megafauna goes extinct and humans are the only large animals left, the far-future civilization uses the human genome as a template to create species intended to fill the niches of bygone bears, tundra grazers, plains grazers and forest apes. Later cases, however, are simply uncanny examples of parallel evolution.
- The New Dinosaurs: An Alternative Evolution has giraffe-pterosaurs (even with giraffe colors), penguin-pterosaurs, koala-dinosaurs (yes, they live in Australia), manatee-dinosaurs, pangolin-dinosaurs (called pangaloons), and even naked mole rat-dinosaurs to name a few. There is also a bird, called the Tromble, that filled the niche of a wooly mammoth in the absence of large mammals.
- Expedition: Darwin IV's fauna has a number of species resembling either extant or extinct Earth species. Gyrosprinters are fast, antelope-like herbivores, unths are large tusked arctic beasts similarly to mammoths, prismalopes are the equivalents of rodents, arrowtongues are large predators resembling a Tyrannosaurus rex, prongheads are pack-hunters similarly to wolves while physically resembling velociraptors, etc. In a bizarre version of this trope, the Emperor Sea Strider is a hundred-foot-tall bipedal creature that inhabits a region of Darwin IV called the Amoebic Sea, walking about on the gelatinous surface and feeding off of it from enormous mouths on the bottoms of its feet. As it's a giant microorganism-eating creature, the largest animal on the world, and restricted to the planet's closest analogue to an ocean, this essentially makes the Sea Strider the Darwin IV equivalent of a whale.
- John Carter of Mars: Some of the fauna of Barsoom (Mars) have clear counterparts on Earth. The Banth is clearly a ten-legged lion, the Thoats are eight-legged reptilian horses and the Calot are stocky pets similar to bulldogs. The White Apes, despite their name, only look like white, four-armed gorillas, but their ecological role is more similar to large predators like bears.
- The Stormlight Archive: Several animals native to Roshar play the role of real-world animals. Chulls are beasts of burden like oxen, axehounds are, well, hounds, songlings are similar to singing birds and cremlings are very much like crabs.
- The Snouters: Form and Life of the Rhinogrades: The snouters generally avert this, as they evolve truly bizarre adaptations unlike any other vertebrate alive today. The Mamontops, however, is a large, shaggy herbivore with prehensile trunks to obtain food, essentially making it a counterpart of a woolly mammoth.
- Alien Worlds (2020): Eden's native animals closely resemble familiar Earth creatures whose niches they approximate — the skittish grazers are essentially rabbits with moth-like antennae instead of ears, while their arboreal predators resemble blue-furred, six-limbed tarsiers.
- Extraterrestrial (2005): Mudpods are essentially alien salamander beavers. They fell trees for food using a constantly-growing saw-like claw explicitly compared to a beaver's teeth, and build dams out of mud to create a network of lagoons that provides rich habitats for other species.
- The Future Is Wild:
- In the ice age five million years in the future, the proximity of surviving animals to their modern relatives means that many strongly resemble real-life creatures. Shagrats are the rodent equivalents of musk ox, the snowstalker is a mustelid resembling both a polar bear and a saber-toothed cat, and the gannetwhales (despite their name) are seal- or walrus-like birds. The deathgleaner is a giant day-flying bat filling the role of a desert vulture.
- 200 million years hence, most examples are less straightforward — the Megasquid, for instance, behaves much like an elephant but is also a part-time predator. However, the flish are flying fish behaving very much like birds, and the squibbons are squids living in trees like gibbons, down to monkey-like social behavior.
- In a notable aversion, 200 million years in the future, the niche of sharks is filled by... sharks, which are every bit as efficient and deadly as they are today or were 400 million years ago.
- Star Trek:
- Vulcan has the seh'lat, the equivalent of an Earth bear. Large wild ones are an example of Bears Are Bad News; smaller ones can be domesticated.
- Klingons have targs, which are like a cross between a boar and a large dog; they can be kept as pets or slaughtered for dinner.
- Star Trek: Deep Space Nine has Cardassian voles, which act like generic vermin such as rats.
- Walking with Dinosaurs: The franchise uses this to some extent when characterizing prehistoric animals.
- Walking with Beasts: The examples here broadly justified, as wooly mammoths and Deinotherium are actually related to elephants and so are Australopithecus to chimpanzees, so it makes sense that they would behave like their modern relatives. Smilodon, however, is portrayed with a social structure identical to modern African lions, which is very unlikely — if nothing else because the lions' social structures are unique among modern felids. The most extreme example in the series is Ambulocetus, which is portrayed as a mammalian crocodile.
- Walking with Dinosaurs: The European species of Iguanodon is given zebra stripes, and makes a zebra-like whinny at one point. Utahraptor, a fast and stealthy predator, is given a cheetah-like coloration with black dots on a yellow base, complete with tear stripes. Anurognathus is treated as the Jurassic equivalent of tickbirds, flying on the bodies of sauropods and hunting insects on their skinnote .
- Walking with Monsters is especially guilty of this. The prehistoric fish Hyneria beaches to hunt amphibians like an orca hunting for seals; Cephalaspis migrates from the ocean to freshwater like salmon, where Brontoscorpio try to catch them like grizzly bears; Diictodon burrow like reptilian gophersnote ; Lystrosaurus migrate in large herds like wildebeest, crossing rivers where they are hunted by primitive crocodylians.
- Ironclaw takes place in a World of Funny Animals that avoids Carnivore Confusion with several species of "lizard" (read: Domesticated Dinosaurs) and Planimal taking the place of fauna. This allows, for instance, boar PC to go on a tusk-melon hunt. There are also constrictor snake gourds, bull-like aurochs radishes, and many more.
- Wanderhome: On Hæth, a World of Funny Animals, the local fauna consist of insects and other arthropods. The playbooks paint this dynamic, as a Moth-Tender can be a pigeon carrying for carrier moths, or a Shepherd can be a ram herding chubby bumblebees.
- Bug Fables: Pillbugs serve as a stand-in for dogs and cats, as they are commonly kept as pets by sapient bugs. Aphids are a stand-in for cows and chickens, as they are commonly farmed for their eggs and dew (which serves as a substitute for milk). Weevils are akin to wolves, being vicious, predatory quadrupedal beasts that even howl. The traveling caravan uses the snail as a stand-in for mules, having it carry their wares during their travels.
- An interesting variant in The Eternal Cylinder, where the Trebhum's planet is filled with bizarre Starfish Aliens unlike anything seen on Earth, and yet many wildlife behave similarly to terran wildlife. Examples include the Onkifurt, a Living Gasbag that broods in nests and hunts from the air like a bird of prey, the Belly Mouth Omnogrom that is a large woodland omnivore similar to a bear, and the insectoid Hophopop that as a small jumping grazer is similar to rabbits and hares.
- The Legend of Zelda: A Link to the Past and A Link Between Worlds have a number of creatures in the Dark World and Lorule that take the place of more familiar and mundane beings in Hyrule, typically moving and attacking in the same way but with more alien and monstrous appearances. For instance, the crow enemies encountered in Hyrule are replaced by Dactos, small Ptero Soarers, while large bats common in Hyrulean dungeons are replaced by Chasupas, giant eyeballs with bat wings. This also occurs for Hyrulean monsters; the octopus-like Octoroks, for instance, are replaced by the more alien-looking, antennaed Slaroks, while the fishlike Zora are replaced the cyclopean Ku.
- Pokémon often uses this trope, with many Pokémon filling niches of real-world animals, though of course All Animals Are Domesticated is in play, with even large powerful creatures being kept as companions by people.
- Warframe: The bat-nosed egg-laying Kubrows serve as a stand-in for dogs while the long-legged Kavats are the equivalent to cats.
- No Evil: Jackalopes are used as beasts of burden, and are treated as the counterpart of oxen or donkeys. Chupacabras, meanwhile, are large, bear- or wolf-like predators.
- Alien Biospheres has enough to gain its own page.
- Amphiterra, being an alternate Earth where frogs, instead of reptiles and mammals, became the dominant species of the planet, has frog versions of many different animals of our timeline, such as the gibbon-like tree frixel, the tyrannosaur-like catastrophic fraggon, and the mammoth-like foaming squander.
- Many of the evolved descendants of canaries become analogues of other birds (such as the falcon-like falconary or the moa-like serestriders), of mammals (the viviparous canaribou or the quadrupedal grazing serezelles) and of non-avian dinosaurs (such as the pseudornithopods or the T. rex-sized, flightless tyrant serins). Eventually, some of the more derived birds cease to resemble avians at all: the changeling birds in particular develop larval states similar to insects, and through further specialization their more derived lineages give rise to permanently aquatic, gill-breathing fishlike neotenic forms or the botfly-like squicks with parasitic larval young.
- The other primary groups of vertebrates in the setting are the tribbets, land-dwelling fish descended from guppies. Their most basic groups are analogous to mudskippers and frogs, while more advanced ones become similar to lizards and snakes. One group, the furry warm-blooded tribbetheres, eventually becomes three-legged mammal-analogues resembling rodents, canids and ungulates. One particular type, the antlears, specifically become a deer equivalent, just with heavily keratinized, branched ears instead of true antlers.
- During the last ice age of the Ultimocene, a giant, trunked bird called the neckbeard and its tribbethere predator the sabertooth circuagodog become obvious expies of wooly mammoths and saber-toothed cats. There is also a herbivorous knuckle-walking tribbethere called the treeskinner that closely resembles a chalicothere.
- Snaiad has shades of these among its creatures: the Kahydrons are akin to canids (though some of the larger species are omnivores similar to bears and one species is a full-on herbivore like a panda), the Fuckers are ambush predators like big cats, and the Allotaurs are akin to rhinos and elephants. However, as the author repeatedly states, all these similarities are only skin-deep, and many vertebrates on Snaiad have no close Earth analog, such as the tiny insect-sized vertebrates called Picotheres. There are also no flying vertebrates: the niche of birds is instead occupied by invertebrate organisms similar to flying slugs.
- Hamster's Paradise has the descendants of hamsters filling every concievable niche on a terraformed, seeded Serina-like planet, such as the grazing ungulopes filling the niches of deer and gazelles, the giant aquatic seavers filling the niches of baleen whales, the predatory carnohams filling the niches of big cats and bears, and flying ratbats filling the niches of birds and bats, with one flightless ratbat group, the blubbats, filling the niche of penguins and polar bears and the scaly, near-ectothermic rattiles filling the niche of many different types of lizards and even tortoises. The oceans in the meantime are devoid of fish, and thus shrish, descendants of krill, fill the niches of various fish such as sardines, sharks, eels, stingrays and flounder.
- Amphibia (the page image): The show is set in a world where frogs and toads are the main equivalent to humans and everything else is scaled accordingly. Thus, the frogs keep spiders as dog-like pets, ride giant snails similarly to horses or donkeys, and farm giant caterpillars with cow-like colorations for dairy (i.e. it's implied, though not explicitly stated, that they create cheese from the caterpillars' mucus). Meanwhile, there are flies that act like birds (actual birds also exist, but they are monstrous predators that eat frogs), and hedgehogs that hunt in packs and cackle like hyenas. Also, an entire episode revolves around a caterpillar acting and looking like a cat.
- Avatar: The Last Airbender and The Legend of Korra's fauna is a combination of real-world animals (penguins, octopi) and Mix-and-Match Critters made from real-life animals. The latter often stands in for their real-world counterparts — turtleducks (ducks with turtle shells) inhabit ponds, polar bear dogs are fearsome predators, et cetera. In one scene, Team Avatar is very confused that the Earth King's pet bear is a regular bear and not a Mix-and-Match Critter.
- The Flintstones: The eponymous family has a sauropod dinosaur acting like a dog and a saber-toothed cat acting like a house moggy. Other prehistoric animals replace objects, such as vehicles and household appliances.
- Futurama: In the 31st Century, owls have taken over the niche once filled by vermin like mice and raccoons, and can often be seen coming out of holes in walls. Cattle, which are stated to be extinct, have been replaced by giant beetle-like, black-and-white spotted alien creatures called buggalo.
- OK K.O.! Let's Be Heroes: Miniature dinosaurs are the main fauna of the show's world. Pterodactyls soar the skies like sparrows or pigeons, while small sauropods and ceratopsians skitter around like squirrels. Gar's Bodega even has a baby T. rex as a pet.
- Silly Symphonies: "Merbabies" has a circus parade scene where aquatic animals appear in the roles of typical circus animals. There are carriage-pulling seahorses, octopuses lumbering like elephants (with one tentacle acting as their trunk), crabs swinging in a cage like apes, a tigerfish with black and yellow stripes roaring like an actual tiger, and snails resembling seals, balancing pearls like balls on their noses.
- Spongebob Squarepants uses this mostly for comedic effect. There are worms in place of dogs, snails in place of cats (although there is also a breath-holding Funny Animal Superhero cat named Kenny in one episode), seahorses in place of horses, scallops are birds (they even chirp!), and jellyfish in place of bees.
- The numerous times anteaters have evolved is an excellent example of how convergent evolution works: many unrelated mammals have independently evolved narrow snouts, powerful curved claws and long sticky tongues for feeding on ants and termites and breaking into their hives: these include the true anteaters of South America (distant relatives of sloths), the aardvarks of Africa (a distant relative of elephants and manatees), the pangolins of Asia (scaly mammals thought to be related to carnivorans more than anything else), the echidnas of Australia (egg-laying monotremes) and the numbats (marsupials).
- The most common large, herding plains herbivores in Africa are antelopes. In Australia, however, this niche is instead filled by kangaroos. Antelopes and kangaroos also fill similar niches to deer in wooded environments, and kangaroos were often compared to deer in the journals of the first Europeans to visit Australia.
- The aye-aye lemur is in a way a Madagascan equivalent of a woodpecker, as it bores through bark with its sharp incisors to feed on grubs and insects that tunnel in the wood.
- The mongoose can be seen as this to the weasel: both are long-bodied small predators adapted to chasing small prey down their burrows. However, they belong to completely different branches of the carnivoran family tree: while weasels are more closely related to dogs, mongooses are more closely related to cats.
- Hummingbirds fill the niche of flying nectar-feeders in the American continent, which is filled by large insects, primarily moths, in other parts of the world. In the deserts of North America, certain kinds of bat fill this role instead, and have developed long, sticky tongues very similar to a hummingbird's to feed on nectar.
- With jaguars native to the Americas, tigers native to Asia and lions native to Africa, and all being the feline apex predators of their respective continents, they can be seen as Fantastic Fauna Counterparts/Palette Swaps of each other.
- Certain prehistoric animals filled niches that modern animals now occupy.
- A notable case are the pterosaurs, who convergently evolved many similarities with birds of today, such as ones that sieved food from water like a flamingo, or ones with throat pouches like pelicans for catching fish. The azdarchids, a group of very large pterosaurs adapted for moving around on land, filled a niche very similar to that now held by cranes and herons, just scaled up to the size of a giraffe.
- Chalicotheres were prehistoric, knuckle-walking, odd-toed ungulates that were essentially horses trying to be gorillas (or from a certain perspective, a literal Donkey Kong).
- The long-necked, long-legged Paraceratherium was essentially a rhino adapted to fill the niche of the sauropod dinosaurs, and giraffes later adopted many of these same traits.
- Aquatic vertebrates have repeatedly developed a number of similar traits — in particular, sharks, ichthyosaurs and dolphins are habitually used in science textbooks to show convergent evolution. Similarly, the elongated primitive whale Basilosaurus was essentially a mammalian mosasaur.
- Prionosuchus, a large Triassic amphibian, greatly resembled a crocodile and likely filled their niche as aquatic ambush hunters ages before the true crocodiles evolved.
- Many Mesozoic mammals and protomammals are very similar to modern species. Examples include the aquatic Castorocauda that had a paddle-like tail similar to a beaver, the gliding Volaticotherium that glided like a flying squirrel, or the stocky dinosaur-eating Repenomamus that are similar to honey badgers of today.
- This trope particularly became a major cliche in artistic portrayals of dinosaurs: Pteranodon was often depicted hanging upside down like a bat, Deinonychus was usually portrayed hunting large prey in packs similar to modern-day wolves, and sauropods were often represented as essentially being reptilian elephants (or hippos, wallowing in shallow water), to name the most common examples. Many of these artistic tropes have since been debunked by new discoveries, but many of them still persist in popular culture and the public imagination.
- African wild dogs can be seen as an African equivalent to gray wolvesnote . They are both intelligent social canines with rivalries with big cats (mountain lions for wolves, lions for African wild dogs.) They have similarities in pack structure, with packs being centered around a monogamous pair, and older offspring either dispersing or staying to help raise younger siblings. African wild dogs hunt antelope, which are superficially similar to the deer wolves hunt. You can also argue that spotted hyenas have some similarities to wolves, especially the extinct dire wolf, although they are not actually canines.
- Mammalian carnivores resembling dogs have evolved so many times in the fossil record that it probably deserves a term like carcinization (caninization?), with mesonychids (carnivorous ungulates), creodonts (primitive mammal carnivores), Tasmanian tigers (marsupials), amphicyonids (the "bear dogs") and hyenas both modern and extinct being examples of animals that assumed a form uncannily similar to true canines. Even the gorgonopsids and therocephalians, primitive mammal-relatives (therapsids) from before the time of the dinosaurs, were rather dog-like in size and body proportions.
- Carcinisation is a very specific convergent evolution phenomenon where crustaceans just keep taking on crab-like shapes, whether true crabs or not.
- It's been theorized that it's possible for some alien life to look superficially similar to Earth life because of convergent evolution. We already see this on Earth with some animal species looking similar to other species they are not closely related to. Starfish Aliens are also probably a thing also. It's not a either/or thing.