We all know that something has to happen to cause the uprising of the Heartless in BBS. Okay, have a theory. It's a little out there so I beg you read and think about it before making judgement. Okay, I think that the first heartless will be created during BBS(the cutscene not the actual game) See, I've heard that this scene is likely very close to the end. So, Kingdom Hearts is very near being completed/opened. The KH shown is very different looking from the one we are used to seeing, so I'm lead to beleive it is fake. Created by some kind of outside darkness. (possibly MX) Now if you'll remember in the scene Ven is left frozen by the end making him defenseless. I think that when KH is opened a massive strain of darkness is going to be released. This darkness will seek out the most powerful (and at this point defenseless) heart. That's where Ven comes in. I think, the darkness will completely overtake the Ven's heart. Thus, creating the first heartless. Like I said it was a bit out there but not at all impossible.
P.S. I also have a similar theory that accomadates the famous Terra=Xehanort theory. Message me if you're interested.
P.S. I also have a similar theory that accomadates the famous Terra=Xehanort theory. Message me if you're interested.