Bone Thwomp

A Bone Thwomp is a species of Thwomp that resembles a large bone inside Bowser's Body. So far, Bone Thwomps have only appeared in Mario & Luigi: Bowser's Inside Story in the Pump Works inside Bowser's Body. Bone Thwomps are rather an obstacle than an enemy, blocking ways that Mario and Luigi must go on their quest. If Bowser drinks water, Bone Thwomps will float, allowing the plumbers to proceed.