Jojo Krako was a gangster boss on Sigma Iotia II in 2268, a planet whose society was based on Earth's Chicago gangster period. A book entitled Chicago Mobs of the Twenties was left by the Horizon, a Federation starship, and the entire Iotian culture had been formed by this one book. Krako's signature style included him wearing a boater.
Krako ran the Southside Territory and was an enemy of Bela Okmyx, the other gangster boss. He had his men kidnap James T. Kirk after he escaped from Okmyx. Krako wanted to be in control of the planet and offered Kirk a third of the action if he provided him with the new "heaters" (phasers). Kirk refused and was confined to a small room. Kirk told Krako that the Federation was taking over and had Krako beamed up to the USS Enterprise to show him what he was up against. Krako and Okmyx were both convinced when a gunfight ensued in the street and Kirk had the ship fire phasers on stun in the surrounding area to demonstrate the power of the "Feds".
Krako became Okmyx's lieutenant, his second-in-command. This helped bind the society on the planet into a loose form of government, and stopped the violence between the two opposing gangs. (TOS: "A Piece of the Action")