GameFreak held a contest or some shit, and you were chosen to be the lucky winner and design your very own mega evolution. You can pick one Pokemon to design a mega evolution for, with a few guidelines:

>The Pokemon should be fully evolved, unless it's a pre-evolved Pokemon with a different stat spread than its evolution (eg Porygon2)
>The mega evolution should have an underlying niche or unique quality. It can be based on a game mechanic already in place (Mega Mawile's Huge Power) or something completely new (Mega Pinsir's Aerialiate), and the more it ties into the Pokemon itself the better (think more Mega Kangaskhan, less Mega Garchomp)
>You can distribute up to 120 stat points amongst the Pokemon's original base stats, as well as reduce one stat to improve another, but you can't go higher than 600bst (720bst for legendaries)

What Pokemon do you give a mega evolution to, and more importantly, how do you make it worth using in a team over other megas?