From the Super Mario Wiki
The Wandering Nomadimouse.
The Wandering Nomadimouse is a Nomadimouse that resides on the path of Dry Dry Desert. He appears in Paper Mario. To escape from the extreme heat, the Wandering Nomadimouse stays under the shade of a palm tree. A letter on a roof in Dry Dry Outpost is for the mouse. He'll give Mario a Star Piece if the plumber delivers the piece of mail to him.
- He's a Nomadimouse. It looks like he's in mid-journey. I bet he has some amazing stories to tell... A wandering Nomadimouse... Roaming the world... no responsibilities... So lucky!