Original Asteroids mini-game:

Reach Zone 1, Level 15, then locate and shoot the green vector graphics asteroid that appears to unlock the classic Asteroids mini-game.

Game Shark Codes:

Infinite Lives 8007F90E 0063

Infinite Armageddon 8107F892 0001

Infinite Items on Pick-Up 8107F8A2 270F

Infinite Points 8107F8FE FFFF