Leo is a dwarf from Tontatta Kingdom who first appeared on Green Bit, where he, along with a group of other dwarves, attacked some Marines. He is the "Tonta-troop leader" (トンタ兵長 Tonta-heichō?) of the Tontatta Kingdom.

Leo, like all the other dwarves, is small and has a large fluffy tail and a pointy nose. He has long brown hair and wears a green hat similar to a crown that has one of its points bent. He also wears a jumper, goggles, boots, gloves, and a tie. He usually carries a gun with him.

(Source: One Piece Wikia)