Mario Kart DS Cheats!

Unlock Leaf Cup: Achieve gold on Shell Cup and Banana Cup
Unlock Lightning Cup: Achieve gold on Leaf Cup
Unlock Star Cup: Achieve gold on Mushroom Cup and Flower Cup
Unlock Special Cup: Achieve gold on Star Cup
Unlock More Kart Choices: Achieve gold on all courses in 100cc, 150cc, or 150cc (mirror) Nitro Grand Prix
Unlock 150cc Mirror: Achieve gold on 150cc Retro Class (all courses)
Unlock Daisy & Dry Bones: Achieve gold on all courses 50cc Nitro Grand Prix
Unlock Waluigi: Achieve gold on all courses 100cc Nitro Grand Prix
Unlock ROB64: Achieve gold on all courses 150cc (mirror) Nitro Grand Prix. Alec Ritter maintains beating just the Nitro cups unlocks ROB.
Unlock Final Mission: Achieve one ranking on all courses for all missions one through six