aaahhh. the million dollar question. will anybody ever know? this has been asked so many times and no answer. supposedly the MK staff dissmissed it as pretty much nothing on fight night if i remember right.

Well the Key unlocks some door in the Village, and the Ninja Star is used when you kill Shao Kahn by throwing it through his male parts and watching him lay there and bleed to death in about 2 minutes.