go to walmart or the craft store - or even staples - look for iron-on transperance paper you can put through your home computer.
find disney clip art on the internet, add text, make sure you flip your design so it is a mirror image - print on the iron-on paper and then iron it to a store bought pillowcase.
if you are having the characters sign - look for sharpies or fabric markers - you might want something hard like a clip board to put under the pillow case while they sign it - also put a piece of cardboard in the middle so the markers dont bleed all the way through.
is this clear - pm me with any questions
jennifer