He's captured Mario and his friends in his pursuit of a crystal that the group collected when it fell from the sky, and he doesn't hesitate to shrink them to miniature size to get rid of them and get his hands on the other four crystals. The mini-heroes have to find the crystals before he does, making their way through giant environments filled with enormous creatures. The single-player campaign takes place in five different settings, each of them ending with a boss. As usual, players have to collect coins and stars, at the same time escaping dangers such as Piranha Plants and other classic creatures from the Mario universe.
One night, five mysterious Sky Crystals fall to Earth. Mario discovers one and eagerly shows it to his friends. Suddenly, a surprise invitation arrives from Bowser: “Hey, chumps! I'm throwing a Big Bowser Bash to apologize for being such a jerk!” Naturally, everyone is suspicious, but the promise of free food is too tempting to resist. They head to Bowser’s Castle, hoping for a party, but it's a trap. Bowser steals the Sky Crystal and uses a new device called the Minimizer to shrink everyone down to tiny size. With four Sky Crystals still missing, Bowser launches the mini-sized heroes to the far edge of the kingdom to keep them out of his way. Their adventure begins, small in size and facing a world full of giant challenges.
