From the Super Mario Wiki
“Greetings! Name's Flimm. Freelance Sales Freak, owner and proprietor of this shirt.”
Flimm, a.k.a. Freelance Sales Freak, is a traveling merchant from Super Paper Mario much like Charlieton from the previous game. His Flopside counterpart is the map-selling Flamm, and together, their names are derived from the word "flimflam", which means "a swindle". Flimm sells many rare items not found in stores, for example a Thwomp Catch Card. He is found on the B1st floor of Flipside. He also may appear in the Flipside and Flopside Pit of 100 Trials at every 10th room. It is unknown how he progressed through the pit. Flimm's sell prices for his items are 75% of what they would normally be, if they have a sell price at all (Turtley Leaf and Golden Leaf, for example, cannot be bought) and this applies to all catch cards. Even the Shooting Star is 75% of what he would sell it for in The Pits of 100 Trials. In the Flopside Pit of 100 Trials, Flimm will occasionally sell things for 200% of their normal sell price. This can make it difficult if the player was only prepared to buy items at their normal price.