How do you find fawful when he takes over peach's castle?

In "Mario & Luigi: Superstar Saga," to find Fawful after he takes over Peach's Castle, you must first progress through the game until you reach the Beanbean Kingdom. After encountering various challenges and enemies, you'll eventually track Fawful to the castle's interior. Look for clues and follow the story progression, leading you to confront him in a boss battle. Defeating him is crucial to advancing in the game.