Town Koopa Bank
From the Super Mario Wiki
When the player decides to stop here, they will meet Koopa, the guy who runs the bank (hence the name). He is in need of help, for someone has just stolen all the coins from the safe. His quest, Probably A Robbery?, is a mystery where Shroomlock comes by to help. After Koopa gives him the details, Shroomlock asks the player to interview the three suspects: Goombob, Paratroopa, and Mr. I. Solving the case will reward the player with the Gaddget, Card Trick.