Silver Coin Challenge
From RWP Wiki
In Diddy Kong Racing and its port, Diddy Kong Racing DS, Silver Coin Challenges are races that require you to collect eight silver coins with the Nintendo 64 logo imprinted on them while still finishing the race in first place. To unlock a Silver Coin Challenge, the player must first complete the courses in a world's lobby by placing first, then beating the world's boss in a race. Once all of the Silver Coin Challenges are completed in a world, the player then may face the world's boss again to earn a piece of the Wizpig amulet, which in turn turns a quarter of the stone Wizpig face into a realistic depiction of the Future Fun Land swine himself.