Keys appear in Yoshi, after the player clears levels 22 through 24 of the B-Type game, rewarding the player 1,000 points.
In Super Mario World 2: Yoshi's Island, its remake, Yoshi's Island DS, Yoshi's New Island, Yoshi's Woolly World, Poochy and Yoshi's Woolly World, and Yoshi's Crafted World, keys can be collected and carried like the Yoshi Eggs, taking up one space of the player's maximum number of them. They can be used to unlock Mini Battle houses, locked doors in castles and Corks that block pipes. Additionally, during the cutscene following the defeat of a castle boss, a large key appears and unlocks a keyhole.