Why grover give Percy a card?

It seems you're asking about the character Grover Underwood from the Percy Jackson series and a "card" he gives Percy. However, there's no mention in the books of Grover giving Percy a card in any specific instance.

To help me understand what you're referring to, could you please provide:

* The specific book or chapter where this happens: This will help me narrow down the context.

* What kind of card are you thinking of? Is it a playing card, a greeting card, a membership card, or something else entirely?

With more information, I can give you a more accurate answer!