Mario and co. first land in the Lava Pits while pursuing Bowser Jr. and Spawny and attempting to directly stop the vortex. After exiting a mine, Mario and co. then fight Mecha Jr. and free Spawny, while Yoshi joins shortly thereafter. Venturing into the deeper part of the lava pools, they encounter the physical Megabug, which immediately captures Spawny and creates Bwario, Bwaluigi, and the Lava Queen. After defeating the threesome, Mario and co. then suddenly find that the Megabug had merged with Bowser to form MegaDragonBowser. After defeating MegaDragonBowser, the Megabug is subsequently defeated, thus restoring peace to the Mushroom Kingdom. After that, they teleport back to the Mushroom Kingdom, along with a new Rabbid Peach statue. Rabbid Peach then takes a selfie with the friends, and they all live happily ever after.