Mario & Luigi: Bowser's Inside Story is the third game in the Mario & Luigi series of games. Players control Mario and Luigi simultaneously in the side-scrolling platform environment of Bowser's body, while also controlling the Koopa King himself in the top-down world of the Mushroom Kingdom. Similar to games like Earthbound, enemy encounters are seen as actual enemies that players can avoid or attempt to strike early. The actual battles are a combination of turn-based menu attacks, and timed reactions to enemies during battle. By watching the way an enemy reacts, you can anticipate their attack and avoid it or counterattack.

A dreadful disease dubbed “the blorbs” has begun to spread throughout the peaceful Mushroom Kingdom, causing the citizens to balloon up and roll around helplessly. With even the Star Sprites at a loss for what to do, Mario and Luigi set out on an adventure to find the cure! And then there’s everyone’s favorite brute, Bowser, who, as always, tries to abduct Princess Peach, only to be thwarted once again by Mario. Angry at his defeat, he meets a shady merchant deep in the woods who gives him a “Lucky Shroom,” with the promise that it will make him really strong. “Strong enough to beat Mario?! Really?!” Bowser swallows the mushroom in one gulp…and instantly starts inhaling anything and everything around him! Somehow he arrives at Peach’s Castle in this state and ends up inhaling the Mario Bros. because of the mushroom’s power. What’ll happen to the Mario Bros. inside Bowser’s body? And what about the fate of the Mushroom Kingdom?