Mario and Luigi Bowser's Inside Story

The game switches between three characters. Mario and Luigi are found together inside Bowser for the majority of the game, exploring 2-D platform-style environments inside various locations of his body. However, battles are still turn based, and are initiated by coming into contact with enemies. Bowser explores the Mushroom Kingdom in a 3/4 overhead-view world, much like previous Mario & Luigi games. After a certain point in the game, Mario & Luigi can go outside of Bowser's body to explore the overworld as well. They can then use pipes found throughout the land to return to the inside of Bowser's body as necessary.
The battle system from the previous two Mario & Luigi games has returned for this installment. In addition to Mario and Luigi, Bowser is now a playable character as well. Bowser's battle system is similar to Mario and Luigi's, but Bowser fights alone and has more advanced stats than the Mario Bros., and Bowser gains the ability to consciously inhale certain of his enemies, enabling Mario and Luigi to fight the enemy inside Bowser.