Years ago at an unknown time and place, a movie producer accidentally dropped an action movie film reel in toxic waste. That movie was then cancelled because of budgetary reasons.
One day a stunt man was watching a copy of that cancelled project, it was full of stunts and action and guns and stuff. It was a movie that involved fighting of crime and other such bad things. He was super psyched and decided to use his stunt moves to fight crime. He was going to have a cool base of operations (B.O.) and was going to do flips and shoot bad guys and maybe use a sword like a katana. He was going to be the most powerful super hero ever.
He would forever be known as Stunt Man.