HT Games
You don't actually unlock individual tracks in Mario Kart Wii—all 32 courses are available from the start. However, two features might make it seem like you're unlocking new content:
Earn 150 stars in Grand Prix races to unlock Mirror Mode, which flips every course horizontally. This adds a fresh challenge by reversing familiar layouts.
Only the first four cups (Mushroom, Flower, Star, Special) are initially accessible. Complete them in order to unlock the remaining four cups (Shell, Banana, Leaf, Lightning).
In short, every course is playable immediately. Progression simply reveals new ways to experience them.