Carrot

Carrot is an item that appears in Super Mario Land 2: 6 Golden Coins. It transforms Mario into Rabbit Mario, but Wario also uses it to transform into Rabbit Wario.

Carrots later appear in Mario Kart Arcade GP 2 as items. However, these carrots have bunny ears atop them.

Carrots also appear in Super Mario Advance (and strangely not in the original Super Mario Bros. 2 and other remakes of said game) as platforms that would bounce up out of hills and help Mario and company reach higher lands. They only appeared in two levels, though.