Darius Dun is a recurring antagonist in the TV show; Teenage Mutant Ninja Turtles: Fast Forward. He's Cody Jones' uncle and the CEO of O'Neil Tech. He's also the one responsible for creating the Dark Turtles. Cody says he hates being called "fatty" in one episode. In issue #64,Splinter offers to spare Dun's life if he surrenders all of his assets to the Foot Clan, but Dun refuses.
However, due to the TV show's cancelation, it's unknown what happened to Darius. It's possible that he got arrested for his crimes.