From the Super Mario Wiki, the Mario encyclopedia
Fondest Hopes is a Flopside card shop located on the first floor in Super Paper Mario and is the Flopside variation of Catch a Dream, Flipside's card shop. The store owner is Boodin, and according to Tippi, his "weekend adult friends" would come to Fondest Hopes to play card games with him.
Mario, Peach, Bowser, and Luigi can buy Catch Cards and Catch Card SPs at Fondest Hopes. Unlike the Card Bags sold at Catch a Dream, the player is able to find out what is on the card before buying it, and the price varies depending on the rarity of the card. Just like his Flipside counterpart Hoodin, Boodin will also buy cards from the players, refunding the card at a price based on its value. The rarer the card, the bigger refund he supplies; the more common the card, the less the card is worth.
Any card except for the main character cards and their dark counterparts can be bought here, though only a limited number are available for purchase at once, with the selection at any given time being random.