I know that it's probably weird that I have never played any of the Pokémon games -- I seldom play JRPGs myself much -- but I'm still interested with the Pokémon lore and setting, as well as its potential to be a template for fans to write stories with. To be fair, people come-up with their own lore and/or headcanon all the time, which may or may not be compatible with the official Pokémon canon. And that's the beauty with headcanons: we get to come-up with our own explanations of how and why the official canons are the way they are. (Until a new game get released, which could invalidate that headcanon -- that's what retcons are for.) Please note that this only my kind of headcanon for the Pokémon series, which may or may not contradict with the established lore.

To be fair, not even the Pokémon canon is consistent across franchises. To date, there are several "official" Pokémon canon that contradict each other: the Pokémon games, the anime TV and movie series, the Mystery Dungeon series, some fringe Pokémon manga that got released now and then, the Detective Pikachu series and its live-action adaptation; and so on. Out of all of these, the Mystery Dungeon series appears to be the most popular of all, especially within the furry fandom, largely because it's the one Pokémon setting that's devoid of humans (not including those who were originally humans, like the main character of each game). So the Mystery Dungeon continuity is the one that people make the most headcanons out of.

In this headcanon of mine, Pokémon can be categorized between two groups, based on how they were born into the Pokémon world: the egg-hatched, and former humans.

The egg-hatched, as the name suggests, are Pokémon born from an egg. They're the most common type. Pokémon born this way are always the pre-evolved form of the mother that laid the egg.

By contrast, former humans are Pokémon who were once humans in their previous life. Former humans are rarer; they're rarely encountered, so much that many Pokémon think of their existence as a legend. Unlike the egg-hatched, former humans were not born the same way: they would suddenly appear into the world out of thin air, typically after a bright light, and it's seemingly random. With the exception of the Legendaries, they can also be of any Pokémon species, including which specific evolution, typically based on their personality and desires in their human life. Circumstances of how it happened varies: maybe the human died, and they found themselves waking-up reincarnated into a Pokémon. (The majority of Ghost-type former-human Pokémon are of that variety.) Or maybe they got cursed into becoming a Pokémon themselves. Former humans tend to retain some or all memories of their previous life -- the most prevalent is the Yamasks, which explains why the majority of Yamasks have vivid memories of their human life. In fact, in my headcanon, all Yamasks are former humans, due to their official Pokédex entry stating that Yamasks were indeed humans in their prior life.

Former humans can be distinguished from the egg-hatched in a number of ways. For one thing, only a human can evoke the power of a Mega Stone, the stone required for Mega Evolution -- this power also extends to that of former-human Pokémon, who can transform themselves into their Mega Evolution form at will with the Mega Stone in their possession. In addition, former humans are "not used" to their Pokémon bodies that they are now trapped in -- they can be seen fumbling around, having an unusual fascination for their own bodies (especially the ears and tail), or attempting to try to walk on their hind legs for Pokémon who cannot normally walk on hind legs. They would need training to learn how to properly deal with and control their Pokémon bodies and the powers that come with it. (That doesn't happen with egg-hatched Pokémon, as having full control over their bodies comes naturally for them.) If they can be frequently seen playing around with their own Pokémon body parts, in near-obsessive frequencies not normal for a typical Pokémon, chances are high that they could be former humans. Some, especially those with vivid memories of their former human life, may also repeatedly insist that they're actually humans.

Why am I presenting all this? Well, it's because I've been thinking about coming-up with a backstory for my Lopunny Pokésona. He began appearing in the world as a Buneary confused and disoriented; some several Pokémon discovered him collapsed near their doorstep, so they nursed him back to health, and they became friends afterwards. (Canonically, these would be my friends' respective Pokésonas.) Several adventures later, and he would inevitably evolve into a Lopunny... and now, he finds himself having to drag around these giant heavy pair of floppy ears attached to his head that seemed more trouble than they worth. Being a former-human Pokémon, even the mere touch of those ears is an overwhelming feeling for him. It took him a while to get used to his evolved form, and even then, getting his ears touched still leaves him giddy -- for that reason, he only allows his most trusted friends to touch his ears as they please. Admittedly, that latter aspect was lifted directly from my usual critter fursona, since my Lopunny Pokésona was also supposed to just be my critter fursona if he's a Lopunny.

So yeah, I tend to like coming-up with my own headcanons, too. However, I also wanted my headcanons to be respectful to the original lore of the worlds I'm basing them from. And it's admittedly one huge excuse to come-up with a backstory for my Lopunny Pokésona, if he ever shows-up in any stories that I could write in the future.