Crab

Crabs are a species of animals found in a few Mario games. In the Mario Kart Series, crabs can be found mostly on beach stages where they walk left and right. Driving over one will make the player spin around.

In Super Mario Galaxy, there are red and blue crabs found in many beach galaxies. To defeat them, Mario must jump on it or Star Spin them to put them on their guard--it will deal no damage, but cause them to retract into their shell, allowing Mario to circle behind them and Star Spin their weak point for massive damage. Blue crabs are more skittish and when defeated give out 1-up Mushrooms.

There is also a crab-like monster known as the Sidestepper in the original Mario Bros. arcade game, which looks basically the same but acts differently.