It's been quite a while but I finally come up with a theory on Eevee and Eeveelutions' theories. Things will be much deeper than most of you expected. Spoiler Eevee is an alien Pokémon species not native to the Pokémon World originally. Eevee was said to be able to adapt to some climate, geographical, dimensional, technological and many other conditions thanks to the unstable, adaptive genetic codes. They can also evolve into certain Eeveelutions at their will, and certain Eeveelutions, like Espeon and Sylveon, look quite alien despite their Japanese origins told by folks in the past (Espeon being Nekomata Seijin (猫又星人), Sylveon and Umbreon are alien moon rabbits). The highly-transformable genetic code is why Eevee species are not native to the Pokémon World originally. Also, Eeveelutions originally have dangerously high powers and intelligence that can even compare to certain alien Pokémon, such as Ultra Beasts, and despite their mammalian appearances, Eevee and their Eeveelutions are technically alien mammals. Also, due to unstable genetic structures, they're originally having secondary Egg Groups aside Field, like Fairy and Amorphous (which explains Eevee's alien structure behind cute appearance), and can be able to breed with Fairy and Amorphous-group Pokémon! Eevee in Pokémon World were highly (and painfully) terraformed that they lost the secondary Egg Group and as such, they're exclusively in Field group unlike their alien Field/Fairy or Field/Amorphous brethren. They also had their powers halved due to terraforming. If you played the earlier main games, you can notice Eevee's an exotic Pokémon which were made as gifts. But they're becoming a little more common in later main games, which might also suggest their alien origin. And if you have played Pokémon GO, a mobile phone spinoff, you might notice that Eevee's a common and popular Pokémon who's constantly adopted by people as pets in that game (or in real-world, for that matter if Pokémon really exists in real-life). But Pokémon GO's case is a different story. In Pokémon World in main games, the Eevee species might be planning an alien invasion via infiltration, and they tried the best to not letting any regular Pokémon (like Pikachu) know their alien origins. Even humans didn't realize Eevee's an alien Pokémon not native to Pokémon World originally, which suggests Eevee's highly-masqueradable nature despite being painfully-terraformed in the Pokémon World (which might be also the same case in Pokémon Mystery Dungeon World). It's also worth suggesting that the gender ratio for Eevee in Pokémon World is heavily male-biased, due to males being more common than females in military science fiction and real-life military, and there are more males joining the Eevee alien invasion into Pokémon World. The gender ratio for Eevee in extraterrestrial planets are uncertain, but some have reported that the Eevee species, which weren't originally native to our Pokémon World, had their genders equally distributed. Their skewed gender ratio is due to their invasion into Pokémon World being more male-biased. So far, I will finish the theories for now. But, your cuddly, adorable cat/dog/fox/whatchamacallit Pokémon might be an alien Pokémon not native to Pokémon World in the past. So, what's your thoughts on this alien theory? No ultra-negative replies, please!