Unlock the following racers by performing the corresponding tasks:

RACER - HOW TO UNLOCK
Fake Crash - Complete the Purple Gem Cup in Adventure mode.
Komodo Joe - Complete the Blue Gem Cup in Adventure mode.
N. Tropy - Defeat N. Tropy's ghost on every track.
Papu Papu - Complete the Green Gem Cup in Adventure mode.
Pinstripe - Complete The Yellow Gem Cup in Adventure mode.
Ripper Roo - Complete The Red Gem Cup in Adventure mode.