Bowser

Bowser is the main antagonist of the Super Mario Bros. franchise, and assuming the role of villain of Super Mario 64. He is a large turtle-like creature that can breathe fire. He has his own type of level in Super Mario 64, as Bowser levels. Bowser levels are linear levels the player must traverse and reach the end of, and then have a boss fight with Bowser. These levels unlock new floors. There is oddly no Bowser level for the Second Floor, with the Third Floor being unlocked after collecting enough stars. Floors unlocked by Bowser levels include the Castle Basement and Second Floor, the third Bowser level unlocking the ending of Super Mario 64. These Bowser levels are Bowser in the Dark World, Bowser in the Fire Sea, and Bowser in the Sky.