Don Leo is a old crime boss who operates in Gotham City. He is also an art enthusiast.
In 2016, Don Leo attempted to take over into the Joker's territory in Gotham. However, he was captured by Joker himself and taken to an apartment where the Clown Crime and Harley Quinn lived. Joker taunted Don Leo and explained his plans to take over the criminal underworld with Harley at his side. The Joker was prepared to brutally bash in Don Leo with Harley's baseball bat, but she planned to torture and kill Leo in order to send a message to other crime bosses in Gotham.