Winged unicorns

Let's be completely clear: WINGED UNICORNS ARE NOT ALICORNS.

A pony fetus naturally starts as a winged unicorn, and up until two months (or thereabouts) all ponies are winged unicorns. Normally at the two month mark the pony's personal magic kicks in; the wings fold back in to form three extra ribs for nonpegasi, the horn dissolves into the bloodstream to grant nonunicorns magical endurance, or both of these events happen and they become an earth pony. On the rare occasions that this doesn't happen, you end up with a winged unicorn coming out; a few of them are even lucky enough not to have their internal organs crushed coming out the tract and become unusual and frail members of society.

At least that's my headcanon. Now, STATS!

Interesting theory, blatant disregard for headcanon thread notwithstanding. Can't help you with stats, as I cannot say I yet share this idea, and as such have no intent on implementing them in the game.

Didn't notice the headcanon thread until after I posted this.