The Mob Boss is the leader of the New York Mafia and a very opportunistic individual who prefers acting from a position of strength. He only stepped into the spotlight when the Foot Clan, the most feared criminal organization in the city, threatened to lose its supremacy over the city after the Turtles defeated the Shredder. He then tried to seize dominion over the city in the resulting power vacuum among the gangs.
During his actions the mob boss, along with his deputy Weasel and his people, crossed paths several times with the Turtles, who were forced to act against his machinations. The situation only changed when Karai arrived from Japan in the name of her adoptive father and finally brought the leadership of the Foot Clan under control. The fate of the Mob Boss after the events of City at War remains unknown.
The Big Mob Boss first appeared in Season One of the 2003 TV Series in the episode called Lone Raph and Cub. He is the leader of the Mafia and a very good fighter. He took Raphael down pretty quickly until Tyler helped a blind Raphael defeat him in battle. After this he's not seen again until Season Two in the City at War episodes. He's seen working with Dr. Baxter Stockman and had him create several machines to help him take over the city. After that failed he's not seen anymore in the series. Its unknown what his real name is.