Kinoko

Kinoko is a former prisoner on Level 5 of Impel Down and a member of the Buggy Pirates.

Past
At some point in his life, Kinoko was sentenced as a criminal and imprisoned on Level 5 of Impel Down.

Impel Down Arc
Kinoko watched over Monkey D. Luffy after he was thrown in Level 5 by Magellan. He was disgusted by Luffy's desire to save Ace and told him that he should only care about himself. He and the other prisoners escaped after Bentham saved Luffy and left behind the cell keys.

Later, Kinoko was seen among the prisoners following Buggy who later joined his crew.