It's possible you're thinking of a few different things:
* The "Master Ball": This is an item in Pokemon games that lets you instantly catch any Pokemon. You can get Master Balls in Pokemon Pearl, but they are very rare.
* A "Trainer Card": This is a card you get in the game that shows your Trainer ID and your Pokemon team. It isn't called a Master Card, but it's a common feature in Pokemon games.
* A "Trading Card": The Pokemon Trading Card Game is a separate game, and while there are Master Cards in it, they don't transfer to the video game.
Could you clarify what you mean by "Master Card"? I'm happy to help you find what you're looking for!