Quote Originally Posted by Neo Emolga View Post
Most of the characters involved in these games are natural Pokémon that have always lived in these Pokémon-only worlds. The protagonist in these games is a human that has become a Pokémon after being taken to these worlds. However, in some cases, there are a few other humans that have become Pokémon for various reasons:

PMD Rescue Team Red/Blue
Spoiler:
Gengar turns out to be a human that has become a Pokémon as a result of the Ninetales curse.

PMD Gates to Infinity
Spoiler:
As it turns out, you're not the only human that has become a Pokémon to save the world from the Bittercold that Kyurem is trying to protect. You eventually discover Kyurem has been defeating these other hidden humans and soon enough, you're all that left and all that stands in his way.

(Don't worry about these exceptions too much, though). :P

But generally, these Pokémon-only worlds only have Pokémon and these worlds are all that they have ever known in their lifetimes. Humans to them are the stuff of fantasy and fairytales and to tell them humans exist would be like telling people mermaids and centaurs exist. They know what they are but they're just myths to them.
I guess I had a general idea before. Thanks for filling in the blanks.