This model was derived from Daniel Lilygreen model located here.
I 've altered his interior construction so that whenever shoved around or rolled, he'll stand himself back up, making a really interesting background plaything. His head additionally rotates.
The BB8 Star Wars Droid is an interesting little chap to roll around equilibrium and your desk. For me this was an interesting experiment with physics, perhaps you create your own characters like him and could take this interior construction of this thing.
The interior construction of him can be discovered as a seperate item here.