The game begins with a stork carrying two babies (Mario and Luigi). Kamek, a Koopa with magical powers, kidnaps baby Luigi, knowing that they would cause nuisance to his master, Baby Bowser, in the future. The other falls into the ocean. Kamek, furious at having lost the other baby, sends his servants, the Toadies, to look. Baby Mario, who had apparently fallen into the ocean, actually fell on an island: Yoshi's Island. He landed right on a Yoshi, who finds a map along with the baby and decides to help him find his parents. Kamek spreads various creatures on the island; they are the bosses of the game. Now the playable character is Yoshi, and he must prevent Baby Mario from being captured by the Toadies.
Yoshi's Island: Super Mario World 2 is split up into six worlds. Each world is a section of the island, split up into levels called "World #-#". At the end of each world is a boss. The walkthrough is intended to give specific details to each level. Click here for info on the first level of the game.