So, I've had this theory lingering in my head for quite some time and I decided to show/tell you guys about it and wanted to know what you think. I could be spouting nonsense but I think it could be interesting...maybe...

 

Anyway, I remembered when Sora stabbed himself with the Keyblade of People's Hearts in Kingdom Hearts 1 and that he turned into a Heartless afterwards. Then I remembered that Maleficent was the only other person to be stabbed by this Keyblade. I thought, if Sora turned into a Heartless after being stabbed by this Keyblade, doesn't that mean that she turned into one as well? 

 

Interested now? Yes? No? Well I'm continuing either way.

 

I theorise that Maleficent's dragon form is her Heartless! Sora's Heartless was born/seen at the same place he got stabbed so it would make sense for her Heartless to be born in the same place as well. You might be asking, "But she turned into a dragon in Birth By Sleep, ten years before she was stabbed." This took me some time to think about but then I remembered Sora's Anti-Form. This form is very similar to a Heartless. So I thought that maybe as a 'Somebody' one can turn into something that their Heartless would take shape as. Yes, Sora's Heartless was just a shadow, I know that, but... y'know what I mean, right?

 

If all this was true, then the Maleficent we see in Kingdom Hearts 2 might actually be her Nobody and it would make sense when it comes to her looks, as Nobodies should look just like their 'Somebodies', excluding the exceptions of course such as Roxas and Namine. As we all should know, Nobodies are born in in-between worlds, such as Twilight Town and Castle Oblivion. It's possible that the Mysterious Tower is one as well. (If I'm wrong on this then please correct me.) If this was true, then I think it would be a good, or at least a better, excuse for her return in Kingdom Hearts 2.

 

What do you guys think? Do you think this is nonsense or do you think that I'm up to something?

Nah, it was pretty well explained that Ansem/Riku only used that special Keyblade to unlock her full darkness or whatever. Anti-form isn't really comparable either; it's not what Sora's Heartless form is like, it's just a side effect of him being a Heartless at one point. Maleficent technically never lost her heart, both her heart and body died and came back to life (same deal with Ursula and Oogie Boogie).

Nah, it was pretty well explained that Ansem/Riku only used that special Keyblade to unlock her full darkness or whatever. Anti-form isn't really comparable either; it's not what Sora's Heartless form is like, it's just a side effect of him being a Heartless at one point. Maleficent technically never lost her heart, both her heart and body died and came back to life (same deal with Ursula and Oogie Boogie).

Also, Anti Form is tied to Sora's clothes, it's them enhancing the little darkness he has, same way the form enhance is normal abilities

Yeah, that's one thing that's never been explained.  Unless she became a "somebody" when the worlds returned to normal at the end of KH1.  Not everyone became human as we saw with the Nobodies in TWTNW, but I'm sure quite a few did.  Also, it's not really fair to compare Maleficent to Sora since she's got magic powers and Sora's just a normal boy.  It's an interesting idea though.