Rabbit

Rabbits of the Mushroom Kingdom, much like their "Real World" counterparts, are small, furry mammals with long ears and large hind paws. They're common in the fields and wooded regions of the kingdom. These animals also feature quite prominently in several Mario games.

Super Mario Land 2: 6 Golden Coins
In Super Mario Land 2: 6 Golden Coins, Mario could become Rabbit Mario by eating a Carrot. While in this form, Mario could use his new-found rabbit ears to hover momentarily while falling or jumping.

Nintendo Comics System
In the "Bowser Knows Best" issue of Nintendo Comics System, the Koopa Family has a pet rabbit named Pookie who they often mistreat, but escapes soon after his introduction.

Super Mario 64
In Super Mario 64, a yellow rabbit named MIPS could be found in the basement of Peach's Castle. If caught, he would give Mario a secret Power Star.

Super Mario 64 DS
In Super Mario 64 DS, rabbits feature much more prominently. They are found throughout the castle grounds (and their locations vary from character to character). The designated rabbits for each character have a specific color - yellow for Yoshi, pink for Mario, green for Luigi, and orange for Wario. If caught, they would unlock mini-games for the player to play in the Rec-Room. Special glowing rabbits needed to be caught to unlock a white door in the Character Door room, behind which was a secret Power Star.

Super Mario Galaxy
Though actual Rabbits do not appear in Super Mario Galaxy, a species of cosmic Rabbits known as Star Bunnies appear in the game, however most of them are simply Lumas in disguise.

Super Mario Galaxy 2
In Super Mario Galaxy 2 numerous Star Bunnies can be found inhabiting the Freezy Flake Galaxy and one can later be found on the Starship Mario.