Mega Evolution is a result of the ayy lmaos trying to modify the genetic code of pokemon. Its mentioned that both the ultimate weapon, Rayquaza (who spends most of its time in the upper atmosphere exposed to cosmic radiation) and Deoxys' meteorite. Many Mega evolutions are mentioned as changing the biology of a pokemon or the temperament (such as Mawile growing another mouth or Lucario showing no mercy) The Ultimate Weapon was fueled by the lives of many fairy types, as evidenced on what pokemon show up the most on the routes in Kalos with the gravestones, and some of these Fairy types, like Clefable, are heavily implied to be from another world. Also, the mega evolution symbol is a dna strand. It's all coming together. Also, it's pretty clear that Eternatus is an Ultra Beast based on its design, who also had to modify other pokemon at will, also, for one last loop, Kyurem, who can fuse with two other pokemon at will, was originally one with Zekrom and Reshirem, and that their original resting place and kingdom was in the desert outside of Castelia. It's mentioned that Kyurem came down in a meteorite. What other pokemon can be found here? Solosis, Elgeyem, and Yamask, all heavily implied to not entirely be of this world, and in the basement of the Relic Castle, you can find Volcarona, a pokemon heavily based off of Mothra from the Godzilla mythos, who has fought aliens before, in a worship esque chamber. They've always been here, bros.
