My son has CP and when he got his dynamic stander in preparation for kindergarten - I immediately thought a life size R2D2 would make him the coolest kid in the school. Made with foam board, paper mache, pencil, marker, a lot of patience =).
I made the cylinder to go around the stander. Though my initial idea was to have it on the outside so you couldn't see the wheels on the stander, I would have not been properly proportioned. Then I Googled images of R2D2 (which weren't many that you could actually see detail) and started drawing, and shading, and drawing, and shading....
I set an exercise ball in the top of the cylinder and blew it up to fit snug with the valve underneath. I paper mache'd the exercise ball like 4 layers, and let it dry (like a week +). Spray painted the head, found things around the house to make dome accessorizes.
I really out did myself, and my son WAS the coolest kid in the school.