Chet Rippo

This character appears in both Paper Mario and Paper Mario: The Thousand-Year Door.

Thousand-Year Door
He is located at the entrance of Rougeport Sewers, in a pipe that is accessible only after Bobbery joins up with Mario.

By paying him 39 coins, he can readjust the ranks of the party members (as long as the are not all at their max rank all) or readjust any of your HP, FP or BP, which could be useful to readjust strategies later on the game.