Press L + R at the "Mode" menu, then enter one of the following codes.

Code - Result

B41S0KV - Flying sheep instead of flame
g3mz - Grey game
SP4RX - Orange game
SPYR0 - Orange Spyro
p0rt4l - Purple game
s0yb34n - Rare "o sheep" card
v4n1ll4 - Rare "stone riptoc" card