This is a spherical robot design that I am working on. I intend to use this to create a replica of BB-8 (lots more work to do!). It is about 18" in diameter and very intuitive to control. Be careful taking it in and out of the sphere so you don't break the wooden tabs. I close the "door" of the sphere using duct tape at the moment but I'm working on a latching mechanism.
(ServoCity.com Parts Only)