Larson scammed Goomther with a fake credit card and was going to continue his devious actions, but Goomther reported him to the Trouble Center and Larson started hiding in the back alley of Rogueport.
If the player accepts Goomther's plee from the Trouble Center, Mario and his partners must chase Larson around Rogueport. After he is caught the third time, Goomther appears to act upon his revenge. However, Larson is never brought to his official justice, and will continue hiding in the back alley.
Goombella's Tattle Log
"That's Larson, the Bandit. The word's out on his scam, so he's laying low here. Of course, he wouldn't have to lay low ANYWHERE if he'd just keep his nose clean...You think maybe he just gets a thrill from breaking the law or what?"