Instructions
Click ̶0;Grand Prix̶1; in the main menu.
Choose ̶0;150cc̶1; on the class selection screen. This is the only class where Dry Bowser can be unlocked.
Click a character, vehicle, and drift type to select your racer options.
Finish the Mushroom Cup, Flower Cup, Banana Cup, and Shell Cup. You must place third or better and get at least a star rating for your driving ability. Your placement determines if you unlock more Cups to compete in. The star rating for driving ability is part of the unlock requirement for Dry Bowser.
Finish the Star Cup and Leaf Cup. You must place third or better and get at least a star rating for your driving ability.
Finish the Lightning Cup and Special Cup with at least a star rating for your driving ability. Your placement in these two Cups does not matter for unlocking Dry Bowser, only the driving ability rating.