The Golden Card is key item that appears in the game Super Paper Mario.
Getting the Golden Card is completely optional to the game. To get the Golden Card, Mario must head into The Overthere bar in Flopside and then Flip into 3-D and head past Carson. He will then end up in a hidden room that contains the Golden Card (and a Cooking Disk). The Golden Card will allow the heroes to play the game Hammer Whacker at the Flipside Arcade.