As You Know, mice normally can't talk on Earth.
There is an animal on this planet that has always looked harmless — rabbits or mice or squirrels or hamsters, it doesn't matter. One day, you will be walking your corgi dog Mr. Flufferkins along and suddenly he will look up at you and say, "Thank you, human, for this relaxing walk and all those times you have scratched my chin, but I'm afraid the Nogov 10th Brigade is coming here in five of your Earth minutes to get rid of this small blue planet and replace it with a transgalactic outlet mall. However, this is good news: you can spend your last five minutes secure in the knowledge that everyone will be getting cheaper outlets soon. Well, except the human race, of course, but these things have to be built. Goodbye." And then he disappears before your very eyes, along with every other corgi on the face of the Earth.
You have just encountered the Alien Animal. These aliens don't have green skin or rubber foreheads, they just look exactly like a specific type of animal. Maybe they make up the entire population of that animal on Earth or only part of them. Sometimes they are leaving Earth because they have knowledge about the impending end of the world and sometimes they just like watching television. Just relax and go with it.
This trope is when every member of an an Earth species originates on another planet. If the alien is pretending to be an Earth animal due to looking like one or Voluntary Shapeshifting, it's The Dog Is an Alien. If the alien looks like an animal but isn't on Earth posing as one, it's probably an Intelligent Gerbil. If the alien animals are a certain species of great ape, see Humanity Came from Space. Can overlap with Transplanted Aliens.
Examples:
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Comic Strips
- A Garfield cartoon suggests that cats are invaders attempting to subjugate humanity, and that they are responsible for certain seemingly-mindless actions of dogs and lower-class humans.
- In one Mandrake the Magician story, Narda has a dream (Or Was It a Dream??) about finding out that cats and dogs are two warring alien species; the ones on Earth were spaceshipwrecked here, and have exploited the dumb native humans (specifically, cats the females, dogs the males) to survive in comfort without their technology.
Film — Animation
- Implied to be the case in Lilo & Stitch (2002) as the only reason the Galactic Federation won't destroy Earth is because they use our planet as a breeding ground for mosquitos.
Film — Live-Action
- Good Boy!: It turns out every dog on Earth is actually an alien from another planet, though many have gone native and forgotten they were originally sent to conquer Earth.
- Lilo & Stitch (2025) uses the same joke as above about the Galactic Federation refusing to destroy Earth because we're a mosquito preserve planet.
Folklore
- The chupacabra that feeds on goats' blood is sometimes depicted as a hairless dog-like animal left behind on Earth by its extraterrestrial owners.
Literature
- Animorphs:
- Domesticated dogs are the product of Pemalites bonding their souls with wolves before they became extinct. So that counts. Sort of.
- Not an animal example, but one of the sidestories indicates that broccoli was brought to Earth by aliens.
- In an interview, K. A. Applegate implied that ants evolved from the Nesk, a Hive Mind race that tried to colonize Earth during the age of the dinosaurs.
- One Callahan's Crosstime Saloon story reveals that we find cockroaches distasteful because they are the degenerate descendants of an evil alien race of overlords.
- Cat-A-Lyst by Alan Dean Foster is another one where cats are really advanced and (mostly-)benevolent aliens.
- Daniel X: According to the first book, elephants were given as a gift to Earth from the planet Alpar Nok.
- A fantasy example from Discworld. Nobody on the Disc suspects that dragons come from the moon until they actually get there and find a ton of them romping around. They're still dumb animals, although slightly healthier in their native environment. Intelligent dragons are, of course, imaginary.
- Humanity Came from Space in Dungeon Crawler Carl, it's said that planets seeded with humans usually get dinosaurs as well.
- According to The Hitchhiker's Guide to the Galaxy Trilogy mice are actually higher dimensional beings responsible for having the Earth created as it's actually a gigantic computer designed to calculate the ultimate question to life, the universe and everything.
- In the Maps in a Mirror story "In the Doghouse", dogs one day start speaking human languages and announcing that they're aliens — and nobody takes them seriously; even when they start demonstrating their advanced intelligence by solving complicated math problems and the like, everybody shrugs it off as just a cute trick.
- A variation in Protector: all primates, including humans, are distant descendants of a group of Pak — known to palaeontologists as Homo habilis — whose spaceship crashed on Earth millions of years ago. It is speculated that the radiation from their power plants accelerated their evolution into new species. This is easily one of the largest Artistic License – Biology ever taken by Larry Niven, who usually makes extremely hard science-fiction.
- The cats in the Star Ka'at series by Andre Norton and Dorothy Madlee. Earth cats were colonists from a planet of sentient cats; when Earth got in danger, the advanced alien cats went to retrieve the Earth cats. The trope is also played with when it's revealed partway through the story that some of the Earth cats have degenerated to the point where they can no longer respond to the telepathic summons, and it's implied that these degenerate cats may even now be the mere animals humans thought them to be.
Live-Action TV
- Doctor Who: Cats. Possibly, it's not clear whether they came from Earth and were kept as pets elsewhere or vice versa.
- The finale of Garth Marenghi's Darkplace has alien spores converting a woman into broccoli. Rick guesses that all broccoli must have originated from similar spores that landed millions of years ago.
- Resident Alien: A montage shows that cephalopods came from Harry's planet, which is why he refers to the Chinese restaurant's octopus as his cousin.
Tabletop Games
- In Spelljammer, spacefaring gnomes have bred a staggering variety of giant space hamsters to serve as Fantastic Livestock (and power sources) for their spelljamming ships. One variant, the miniature giant space hamster, is intelligent, sapient, and telepathic. They're sometimes introduced to planets (where they become known simply as "hamsters"), and they prefer not to draw attention to themselves by using their psychic abilities.
Video Games
- Przygody Reksia: The fourth game reveals that the ancestors of all the moles on Earth are actually from Kuran (which would have been known as Kreton back then). They reached Earth in a spaceship that was subsequently destroyed by Reksio and Kretes when they traveled to the prehistoric era.
- In the game Sheep, you have to lead the sheep, who have become stupid in the time they were on Earth, back to their home planet.
- Sonic Frontiers reveals that Chao are actually descended from an alien species known to Earth as the Ancients. After a second attack by The End, the surviving Ancients had their DNA corroded by radiation over several generations until they turned into the Chao.
Webcomics
- While not intelligent, foxes in Jix are, in fact, extraterrestrial. A race of aliens took a group of pre-evolved foxes from the Ambis home-world and deposited on Earth to study divergent evolution on a planetary scale. The pre-evolved foxes remaining on their original planet evolved into Ambis while the ones on Earth (of course) evolved into foxes, making the Ambis the distant cousins of foxes. (In fact, Ambis bear a striking resemblance to foxes.)
- Bees in Skin Horse are an odd instance here. It's initially implied that they were the result of an experiment in Mad Science, as is the case for much of the cast. They, Gavotte included, are in fact from the planet Lovetron, and of differing opinions with regards to going back. They also have no idea why humans love their honey so.
Western Animation
- The dinosaur-like aliens from Chip 'n Dale: Rescue Rangers look like earthling dinosaurs, only smaller and more advanced. During the Late Jurassic Period when they arrived, they ate the dinosaurs' earthling food and became as large as them, but less intelligent.
- Four Eyes!: Alien protagonist Emma states that frogs are originally from her home planet, Albacore 7, and because of this, she can communicate with them.
- The species of highly intelligent (and highly cuddly) cats from Futurama. They're here to enslave and kill humanity, natch.
- The Owl House: Eda tells Luz that giraffes were originally from the Boiling Isles, but were banished to Earth for being weirdos (says the witch who later leaves her detached hand on her magic staff).
- Polly Pocket: In "Area Fifty-None", it's revealed that at least some Earth turtles (including Shani's own pet turtle) are really space aliens.
- In South Park, Earth is revealed to actually be a massive, millennia-old alien reality show. Apparently, every other planet only has one species — a planet of deer, a planet of Asians, etc. — and we're all just forced together so everyone can watch what happens.
