Bet you didn’t about the Gold Karts. How to unlock them? That’s a different story. Here’s the solution by Nintendo Fuse. http://www.wiinintendo.net/2011/11/29/mario-kart-7-unlockables-tips-tricks-cheats/
Mario Kart 7 – Gold Items
– Gold Wheels: Obtain Minimum of 1-Star Rank on all Cups
– Gold Glider: Connect with 100 people through StreetPass or collect 10,000 coins.
– Gold Standard Body: Get a VR higher than 10,000 points or collect 20,000 coins.
– Gold Steering Wheel: Play 100 recent matches, and use the first person gyro controls 80% of the time.
– Gold Wheels: Successfully complete all Cups in 50cc, 100cc, 150cc, and Mirror mode with a “1 Star” or better rank.