Little Skull Mouser
A Little Skull Mouser is an enemy found only in Super Mario World 2: Yoshi's Island that is similar to Little Mouser, but wears the skull of an unknown creature on its head. It jumps around aimlessly and, like most enemies in the game, can knock Baby Mario off a Yoshi's back. Unlike regular Little Mousers, Little Skull Mousers are unable to steal Yoshi Eggs.
When a Yoshi jumps on a Little Skull Mouser's head, hits it with an Egg or spits an enemy at it, the skull it is wearing crumbles, turning the creature into a normal Little Mouser. Unlike many other small enemies, a Little Skull Mouser cannot be defeated immediately by a Ground Pound; instead, the attack has the same effect on it as a normal jump, merely destroying the skull on its head.
