From the Super Mario Wiki
Chet Rippo will upgrade one of Mario's stats by two levels, but downgrade the others one level in Paper Mario, despite his claims that he simply upgrades one with no side effects. Chet Rippo appears in Toad Town near Harry's Shop and charges thirty-nine coins for his services, saying they are normally worth three hundred ninety.
In Paper Mario: The Thousand-Year Door, he does the same thing, though he is more honest (referring to his services as "adjusting" rather than "upgrading" and admitting the downpoints to the use of him, even allowing the player to choose which character's stats get downgraded). Visiting him is slightly more worthwhile in this game, if the player in question is willing to even out his or her stats for a fair price. Chet Rippo can also switch two partners' ranks around. The price for either of these services is thirty-nine coins. He appears in a house in the background of Rogueport Sewers near the main entrance; it can be seen to the left of the Warp Pipe first used to reach the sewer ruins. The player has to use Admiral Bobbery to blow up the wall directly left to this aforementioned Warp Pipe to unlock another pipe leading to Chet Rippo's house in the background.
It is possible that there are two different Chet Rippos. In Paper Mario, he appears to be a pudgy, bird-like creature, while in Paper Mario: The Thousand-Year Door, he looks more like the Shaman characters Merlon and Merlee. As a matter of fact, he may even be related to these Shaman-types (and may even be a member of the fortune-telling clan that names their members after their purposes mentioned by Wonky), although this is unlikely as his name does not begin in "Merl-". Noticeable is that in Paper Mario: The Thousand-Year Door, his hat is a severed upper half of a barrel and his cloak is patched.
In Paper Mario, he's the negative equivalent of Rip Cheato. Both their names are derived from the words "cheat" and "rip off". Both "Chet" and "Rip" are actual names.
Paper Mario: The Thousand Year Door
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