From the Super Mario Wiki
“I'm traveling on business, so everything goes on the expense account! Yes!”
The Businessman, as he is called, is a Ratooey found in Paper Mario: The Thousand-Year Door. He first appears in the Excess Express, happy that he can charge everything to his business account, as he is riding the train for business reasons. On the voyage's second day, he lost his briefcase, which contained early plans for his company's latest invention, Nitro Honey Syrup. He gets it back when Mario finds Zip Toad and exposes him as a fake (although his true identity, Doopliss, isn't actually revealed until after the Businessman gets his suitcase back).
For unknown reasons, the Businessman has a love of chairs that border on outright fanaticism. In fact, his Trouble consists of Mario needing to tell him how many chairs are in certain houses spread out across the world, such as Don Pianta's office and Flurrie's House. The reason for this is because he forgot the security code needed to open his briefcase and the code consists of the numbers of chairs in four houses.