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From Unmariowiki

Pickle, as he appears in SMK.

Pickles are the power source to Mario and Luigi's fireballs. Just by destroying one of these sacred foods, the mario bros. could lose all their power. The pickle was mentioned first in Super Mario: The Cheese Adventure when Bowser complains about a sliver in his foot. He yells out with exclamination, "HOLLY PICKLESAUR MY PICKLING FOOT!" The pickle shattered into pieces in the game Yoshi's Island: The Battle For The Pickle, where all of the yoshi's teamed up to get the pickle pieces.

A different pickle also appears in an episode of SMK. However, this pickle was living, and was an enemy at Tumble Tunnels. This pickle also was Evil Guy's assistant in Super Mario 128. He died, but in the end was used to turn Luigi into a pickle.

A pickle shaped dinausaur also appears, named Yoshi. Little is known about Yoshi, though, and some have stated that his whole existence may be a conspiracy.