Game Freak approaches you - yes, you - and asks you to stat a new Pokémon. Not the actual design, mind you, because they know you spergs would make a talking dick or some shit, but how it mechanically battles. You must work within a 510 BST distribution, but every other aspect is up to your discretion, including typing, ability(s), move pool, etc.

Obviously you can't give a Dragon/Fairy Wonder Guard. Strong or weak, whatever, but aim for being reasonable.