Now that is an interesting challenge. I did an image search for the little critters and I think you could come up with something and just draw the quills in place. Although if time wasn't an issue you could probably make the body a sort of three bubllw roll through with a few extra double ear twists (placed across from each other so the balloon stays straight) as attachment points, and then use 160s as the quills. I may have to play with this idea sometime.
