Use one of the following codes at the character selection screen to play as the corresponding Boss:
Anil 8: Up, Right, Down, Right, Right, Up, Left, Up
Assault: Right, Up, Up, Right, Down, Right, Up, Up
Mayhem: Left, Right, Down, Left, Up, Left, Down, Left, Down
Supervisor: Down, Right, Down, Up, Right, Down, Left, Down, Up, Right, Up
Vitriol: Right, Right, Right, Up, Up, Down, Left, Left, Down, Down