Fat Jack is a heavily overweight thug who wears fingerless gloves and a sleeveless shirt with a lighter jacket and shorts. Fat Jack has a mohawk (and a five o'clock shadow in promotional artwork). He prefers to go barefoot and is never seen wearing shoes.
Fat Jack is said to be a relaxed and laid back person, but is also with a strong attitude. He especially enjoys Ramen, and frequents local Metro City outings.
Fat Jack is a member of the Skull Cross Gang, and is a part of Callman's division. Due to his laid back personality, he is often at odds with his boss and has to commonly keep a look out at work in Metro City's downtown. Despite this, Fat Jack is also in charge of destructive jobs and tasks, including vandalism and thug work, which gets the cops from the Metro City Police Department often muddled and surprised by his personality when they have to apprehend him.
Fat Jack usually moves slowly and attacks by slapping enemies at close range. However, he has a large amount of health and can close with enemies quickly when he charges in with a shoulder tackle.
- Fat Jack's name is a take on the Australian food chain Hungry Jack's, which is known elsewhere as Burger King.