Catch a Dream
From the Super Mario Wiki
Catch a Dream is a card shop located on the first floor in Flipside, exclusively found in Super Paper Mario. It is also the Flipside version of Fondest Hopes, Flopside's card shop. According to Tippi, boys "descend on this place" after school.
The store is manned by Hoodin, who will both buy and sell Catch Cards from Mario, Princess Peach, Bowser, and Luigi. Each Catch Card is sold individually in small bags known as Card Bags. The cost of a Card Bag is ten coins each, with the outcome of the card being random. When Hoodin buys a card, he will judge it based on its rarity. The rarer the card, the more money he'll give the player for the card; likewise, the more common the card, the less money he'll give for the card.
Interestingly, while the Whacka card can be bought here (as a Card Bag), it cannot be bought at Fondest Hopes, making the Whacka card, along with the cards for the Heroes of Light and their dark counterparts, the only cards in the game that cannot be bought there.