Sphero has developed a ball which includes an internal drive system with motors coupled to wheels engaged with the inner surface of the ball. The wheels are continuously engaged with the inner surface to allow for power to the motors to be transferred to the inner surface of the ball. This causes the self-propelled ball to roll and maneuver along a surface.

The ball also includes magnetic interactive components inside the ball. An external accessory is magnetically couple to the ball. The external accessory is shaped like head of BB-8, as shown below.

The ball is able roll and maneuver while the external accessory remains under magnetic interaction with the magnetically interactive components within the ball. The accessory device remains within a constant relative portion or area on the exterior surface of the spherical housing (e.g., a top portion) as the self-propelled device rolls.

US9342073