A topic that people at times talk about is aliens and their existence, beings that seem otherworldly to them. While it cannot or may not be conclusively proven that they exist somewhere in the universe, the plausibility of that existence still makes for something to be pondered. Meanwhile, the world of Pokémon exists in a universe not much different from that of the real world. With that being the case, it is just as plausible that aliens can exist in that universe. And in fact, they do in a way, and the reality is also a lot more complex.
The most well-known case of "aliens" existing - or one of them - is the Mythical Pokémon Deoxys. It has been documented that the Pokémon appeared from space in both the anime (the seventh movie) and the games (the third-generation remakes). While it is a full-fledged Pokémon in many ways, the way it presents itself suggests that the Pokémon has its origins not from the known world of Pokémon, particularly a nether region of space, therefore making it an "alien". Its behavior also suggests a fair bit of hostility as some aliens may be expected to have. It appears as one in a true sense.
More recently, a host of creatures from a different dimension have made themselves present in the island region of Alola. They are, of course, the Ultra Beasts, and likewise they are as much Pokémon as they are "aliens". By the virtue that they came from that dimension, they are "aliens" outright, especially if such a thing were to happen in the real world, no matter how unlikely. They too have been known to show hostility if warranted, which makes their "alien" status even more reasonable. The opening of the dimension is a definite key to this, without which their existence would simply have been passed by.
Of course, for anyone not too well-versed in Pokémon, they might think that the creatures themselves are the "aliens", which also isn't too far out if it were to exist somewhere. They might have arisen through a process called "panspermia" as the distribution of genetic material across space by way of objects like meteors, then they might have mutated and developed into these creatures along with the people they are amicable with. Come to think of it, that same process might have occurred in real life as well, making us (or at least some living elements of the environment) the "aliens". Hmm.
The topic of aliens will always involve some sort of controversy with their hard-to-prove status, perhaps at least until one comes along and reveals its existence, at which point it may not be anymore. For the world of Pokémon, however, there is a reality that involves some creatures that may be definitely regarded as "aliens", and since its and our realities have much resemblance, it may still be possible for us to come upon our aliens in the future. Whatever the aliens involved, the otherworldly qualities will seem to remain quite prevalent.
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