It starts with Waluigi finding the magical Dual Wield Golden Pistols and decides to start destruction. Mario and Luigi have to save the Mushroom Kingdom from Waluigi. Waluigi teams up with King Koopa, King Dedede, and Your Mom to defeat them. The game has multiple playable characters who are Mario, Luigi, Yoshi, and The King of Hyrule. Once you beat the story mode you unlock free-roam mode, which is similar to Grand Theft Auto, in which you can run around killing toads and enemies.