I'll make a few I can go into detail later, right now I'm kinda busy xD

Cuzco Empire/The Emperors New Groove/ No standard Guest, however Cuzco, Pacha and Kronk will indirectly aid the party

Sid's House/Toy Story/ Buzz and Woody. They can combine their abilities to bring out each others potential.

Oahu/ Lilo and Stich/Stich. This movie has a lot of potential for a great level. Since it includes space travel, perhaps a second world can be linked to it.

Mouseland/ The Great Mouse Detective/Basil
I just want an excuse to be able to beat up Ratigan with a keyblade.

Then there is this world I made from the elections.