Rabbits are animals that can be found in game that can gives you a item.

Rabbits: There are 36 total rabbit hidden around the castle (9 for each character) It depends on where they are hidden on what character you play. If you eat or grab one, they will give a minigame for you to play. In the beginning of the game, one of the Yellow Rabbits will have a key you must use to unlock the castle door. Also, when the newsletter about Waluigi being in game, it said you had to defeat the king rabbit to unlock Waluigi (even though it was only an April Fools prank) If you are Yoshi, they will be yellow. If you are Mario, they will be pink. If you are Luigi, they will be green. If you are Wario, they will be orange.