- 1). Start the game and select the “Circuit” mode option with your Wii remote. Select the character and kart you want to race with.
- 2). Complete every course in the Flower Cup and Mushroom Cup, and finish in at least third place to unlock the Star Cup.
- 3). Finish the Star Cup by winning at least third place and you’ll unlock the Special Cup level.
- 4). Win at least third place in both the Banana Cup and Shell Cup races to unlock the Leaf Cup courses.
- 5). Finish the Leaf Cup races and get third place overall to unlock the Lightning Cup, which is the final unlockable course.
Source...