From the Super Mario Wiki
Garson is a helpful character in the game Super Paper Mario. Garson acts much like Wonky of Paper Mario: The Thousand-Year Door and is found underground, just as Wonky. He is found in Flipside Basement 1.
Garson owns a bar called The Underwhere, and Garson can tell the four heroes tips and stories for ten coins a piece. The Flopside version of Garson is named Carson and owns a bar called The Overthere.