Ucantia Defeatus is an enemy class in Super Mario World 2: Yoshi's Island and its reissue, Yoshi's Island: Super Mario Advance 3. Its name is a pseudo-scientific corruption of the phrase "You can't defeat us." Enemies in this class can be defeated only in a certain way and cannot be eaten. They include Piranha Plants, Tap-Taps, Boos, Zeus Guys, Bandits, and the game's bosses.
- Williams, Drew. Yoshi's Island: Super Mario Advance 3 Player's Guide. Page 17.