To truly complete Mario Kart DS, you'll want to unlock every character, kart, and game mode. This involves systematically working through the Grand Prix and Mission Mode. Here's a consolidated checklist to ensure you don't miss anything:

Characters:
- Dry Bones: Win the 50cc Star Cup.
- Daisy: Win the 100cc Special Cup.
- Waluigi: Win the 100cc Mushroom Cup.
- R.O.B.: Achieve at least a 1-star rank on all 7 levels of Mission Mode.
Karts (for all characters):
- Standard Kart: Win all 50cc Grand Prix cups with a Gold Trophy.
- B Dasher: Win all 100cc Grand Prix cups with a Gold Trophy.
- Poltergust 4000: Win all 150cc Grand Prix cups with a Gold Trophy.
- Royale: Win all Mirror Grand Prix cups with a Gold Trophy.
- Gold Standard: Achieve a 1-star rank or higher on all 150cc Grand Prix cups.
Game Modes:
- 150cc Grand Prix: Complete all 50cc Grand Prix cups.
- Mirror Grand Prix: Complete all 150cc Grand Prix cups.
- Retro Grand Prix: Available from the start.
- Mission Mode Level 7: Complete all previous Mission Mode levels.
- Chief Chilly Boss Battle: Achieve at least a 1-star rank on all 7 levels of Mission Mode.
Tips for Unlocking:
- Systematic Approach: Tackle Grand Prix one CC level at a time (50cc, then 100cc, etc.), aiming for gold in every cup.
- Replay for Ranks: If you don't get a 1-star rank on 150cc Grand Prix the first time, replay cups to improve your performance.
- Don't Skip Mission Mode: It's crucial for R.O.B. and the final boss.
Unlocking everything provides a great sense of accomplishment and gives you access to the full roster of options for competitive play.