2. Caesar Clown
Caesar Clown first worked for the Marines, as their scientist. He calls himself the greatest scientist in the world. He did some experiment without anyone knowing about it.
Later, when he was caught by Vegapunk, he detonated a bomb, which killed the entire living population on Punk Hazard and fled from the island. He returned to the island, and joined the Donquixote Pirates to make SMILES for them.