Unlock Gold Parts
Gold Glider - Collect 10,000 Coins (Multiplayer gives players the total amount of Coins collected by all players during each race).
Gold Handle - Use the Wii Handle for 50% of your most recent 100 stages.
Gold Standard Kart - Get at least one star (54 points or more) on every 150cc and Mirror Mode race.
Gold Tires - Beat all of the Time Trials Staff Ghosts.
Unlock Other Racers
In Grand Prix mode, get first place on any Cup at any CCs and it will give one of the 14 Characters at random however you can not repeat the same cup with the same CCs.
Rocket Boost
Press the accelerator button when "2" appears and hold it down for a rocket boost at the start of the race.