From the Super Mario Wiki
Captain Goomba, Captain Shy Guy, and the assisting Lakitu find Larry building his fortress to take over Beanbean Castle Town. They decide to fight him in order to unbrainwash him. After the battle, Larry joins the squad, telling them of four locations he knows that yield a brainwashed Koopaling. Captain Goomba decides to head to Chucklehuck Woods first to find Iggy.