Demon hidden vehicle:
Press Up, Down, L1, L2, Select, Start at the select game screen (main menu). A sound effect will confirm correct code entry. The hidden vehicle will be available in all game modes.

All arenas and tracks:
Press Down, Up, R2, R1, Start, Select at the select game screen (main menu). A sound effect will confirm correct code entry. All the arenas and tracks will be unlocked in time trial and battle mode games.