Enter "TC4D" as a password to unlock more levels and the BMX Superbike.
Enter "QGF7" as a password to unlock training, career, and tournament modes.
Enter "SBPN" as a password to unlock most levels.
Enter "RBKZ" as a password to unlock some career mode levels.
Note: You must have a 2.1 or higher version of the Game Shark to use these codes in a Game Boy Color system.