Wait Darkest are you saying you were drunk when you sang that... IMO any one who sings a rap for 649 is Drunk and or crazy, just inmation trying to do a Pokérap for hundreds or even thousands of Pokémon the Pokémon.
The Animé clearly hinted in Destiny Deoxys that the number of Pokémon is so large that doing all of them in a a Pokérap would be next to imposable and that's only the ones on the world of Pokémon AKA Earth AkA Gaia, and the movie also hints that there may be other planets inhabit by Pokémon and perhaps humans as well.
Hey in a universe that was allegedly created by Arceus with the aid of the Unown who acted like his thousand arms, (In fact it's kind of funny if you think about it Arceus is said to have hatched from an egg my thought is that the Unown are the ones who created the egg.) nothing is to farfetched.
While yes it's true that Game Freak tries to keep things realistic or at list find a balance there of in a would of fantasy were you have fire breathing chickens and Mice that can zap you with a thunderbolt and all sorts of weirdo things that should not be even be possible.
In short the Creators have established the Idea that there are more Pokémon that meets the eyes. in fact if my hunch is right and the orgnal Idea was to have Kanto and jotho be based on Tokyo but geography wise look like three of Japan's prefectures and had they given each region a regnal dex with there one set of starters and Legendary Pokémon well lets just say they would still be doing regions of the Kanto region...
I mean for example I could take the city of Detroit and create 12 regions out of it because that's how many Neighborhoods are in Detroit Mi. oh and FYI Blade read this to get my point.
~Charles Legend