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.

Mario and Luigi: Bowser's Inside Story videos