No, the "Kingdom Hearts" anime would have to relegate itself to just the Disney animated characters, since the anime would probably be produced by Disney, just like "Stitch! The Anime" is. And certainly, Disney wouldn't have characters from other studios appearing in the anime- unless the characters are tied to Disney in a certain way, like Kat from "Kid Vs. Kat". Perhaps somehow Kat's planet could work as one of the worlds in the "KH" anime series. It may be a stretch, but it could be possible.