Black Jack is a mischeivous male pegasus pony that runs the Solitaire Casino. Though no proof of cheating ever occurs, he has an unnatural amount of luck when it comes to such games, and usually wins. He's friends with Cocoa Puff who run's the milkshake bar in the Casino. Although why Cocoa Puff is friends with him despite his rather dark and sneaky behavior is beyond anyone.
Black Jack is a character made by Shirou14, he is not Shirou's main brony persona, but a facet of his main persona's history.