From the Super Mario Wiki
“Heh heh heh... I used my entire allowance on Catch Cards again... But RAARCH! I buy bag after bag, but still NO RARE CARD! Now I'm broke! Is this what people mean when they talk about that 'card debt'?”
Pitta is a young boy living on Flipside's first floor in Super Paper Mario. He's always on the top of the latest and greatest trends in Flipside. Although normally a thrifty person, when it comes to the newest fads, he breaks the bank by spending all of his allowance. In the game, he is obsessed with Catch Cards.
His name could be a truncation of pittance meaning a small amount of anything, but especially money, fitting for Pitta after he indulges in his Catch Card hobby.