From the Super Mario Wiki
Charlieton is a traveling salesman encountered in the game Paper Mario: The Thousand-Year Door. He appears to have a knack for ripping people off, much like Rip Cheato; his name is even a pun on 'charlatan' (a swindler).
He sells items and Badges in the Rogueport Plaza. Most of his items and Badges are pretty rare, and he is the only way for Mario to complete his Badge collection. His prices are also high, but Jammin' Jellies and Ultra Shrooms are sold at 120 coins each, their cheapest price in the game. Charlieton's inventory cycles and changes from day to day depending on the clock on the Nintendo Gamecube and/or the player's progress. Therefore, all items that he sells can theoretically be obtained at any given point in the game, meaning that while certain items may not appear for a while, none of them are permanently missable.
If Mario buys all the things available, he will thank Mario for putting his kids through college.
Charlieton sometimes appears in the Pit of 100 Trials, selling common items like Mushrooms. The cost was greatly inflated, but sometimes Mario would have to purchase the ridiculously priced item to survive in the Pit. The prices would rise as Mario ventured deeper in the Pit. It is unknown how Charlieton got so far in the Pit, since it is required to beat every enemy to progress.
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