Ucantia Defeatus

In Super Mario World 2: Yoshi's Island, the Official Guide from Nintendo Power describes how the Yoshi series has different enemy classes. Of those, one of them is Ucantia Defeatus. Enemies in the class Ucantia Defeatus either can't be defeated or can only be defeated a certain way. Common examples of these enemies include Piranha Plants, Tap-Taps, Boos, Zeus Guys, and Bandits.

Trivia

 * The name is a pseudo-scientific name corruption of the phrase "You can't defeat us".