Forget the first post, download cBliss Tool, use it in a fresh Project M 3.02 gct and be sure to fill the costumes for every character, included Roy and Mewtwo.
Alright! I got it to work! Thanks! 
Thanks again & thanks in advance!

EDIT: OK, now it's happening everytime I choose a custom character. I REALLY need some help, thanks.

ANOTHER EDIT: Uh...the game froze (yet I'm stll able to use the home button) even though I chose original characters (non-custom ones). What's going on? :/