Unibo

In Super Mario Land 2: 6 Golden Coins, Unibō are Urchin-like enemies inhabiting flying and swimming areas. Unibō are nearly indestructible, only being killed by a Star or Koopa Shell. They remain stationary until Mario comes near, at which point they will shake on the spot to make themselves harder to avoid.

Trivia

 * Unibō are very similar in appearance to both Gordo from the Kirby series and Sea Urchins from the Zelda series, and are commonly mistakenly thought to be the same creatures.