Bowser is in his castle, depressed that he can't get the attention of Peach. Later that day, Fawful returns to invade the Mushroom Kingdom. Bowser thinks "If I can beat Mario to defeating Fawful, I'll definetly get the princess's affection! GWAHAHA!!!" So he sets off to defeat Fawful before Mario can.
A rock monster that resembles an Onix
A brainwashed Monty Mole
Mario (final boss)