Yoshi eats a rabbit and unlocks a door to the castle and explores the castle and its courses to find his friends. Scattered throughout the castle are paintings and secret walls, which act as portals to other worlds where Bowser's minions guard Power Stars. By recovering the stars and defeating bosses, Yoshi acquires keys to other areas of the castle and rooms holding his friends captive. He first defeats Goomboss to free Mario who assists him as the two continue searching the castle and collecting Power Stars. Mario then defeats King Boo to free Luigi who then uses his invisibility power to get to Wario's key by defeating Chief Chilly. During the course of the adventure, they tackle three obstacle courses leading to a battle with Bowser.