Pokemon only being based off animals would be boring as ****. The "object" Pokemon and "alien" Pokemon have been around since Gen 1, and they're some of the most creative and interesting designs/stats/typings
In the anime, Jirachi descended from outer space in the Millennium Comet, which is visible from the Pokémon world for only seven nights once every thousand years. The origin of this comet, or Jirachi itself, is unknown, and as such, it is not known if there are any other Jirachi left in existence. It is also based on the concept of wishing upon a star.
It'd be amazing if they did a Generation X / Generation Y special edition game with X containing Fire Red, Heart Gold, Ruby, Diamond, Black, and X, all on one massive game. Y would carry the other half, Leaf Green, Soul Silver, Sapphire, Pearl, White, and Y.
Z would have *Yellow, Crystal, Emerald, Platinum, Black 2 & White 2.
