The Bounding Demons in Lost Izalith are actually made from the same mesh as the lower half of the Undead Dragon minibosses. Neither of the two Undead Dragons ever stand, and the one in the Painted World Ariamis crawls forward and disconnects from its lifeless lower half. There is a glitch where attacking the lower half when you can reach it with a plunging attack will prompt the body to shoot up onto its legs like a Bounding Demon, thus eliminating the need to unlock several doors and pass through a fog gate.