In his evil plot to take over the Mushroom Kingdom, Fawful tricks Bowser™ into eating a magic mushroom. The mushroom causes Bowser to begin inhaling everything around him, including Mario™, Luigi™ and Princess Peach™! Do the Mario Bros. have the guts to rescue Peach and escape?

• Players are in control of two separate storylines. One features Bowser and his efforts to stop an arch-villain from taking over his castle. Meanwhile, inside Bowser, the microbe-sized Mario & Luigi must muscle their way through challenges and keep their nerve if they want to find a way out. They take action to control Bowser from the inside – but without his knowledge.
• Players can switch between storylines at will. What happens inside Bowser affects what he’s doing on the outside. Sometimes Mario & Luigi must solve puzzles and challenges behind the scenes to help Bowser overcome various obstacles and advance the plot.
• Players must make well-timed button presses to enhance their performance during battles and challenges. In some battles, Bowser grows so large that players must turn their Nintendo DS or Nintendo DSi™ system sideways, blow into the microphone or tap on the touch screen with the stylus to keep up with the action.
• The game features the same hilarious dialogue that has been the hallmark of the Mario & Luigi series.