Level Select
Go to the options screen and highlight "Password" and hold select. Then press Triangle, L1, Square and release select and press Triangle, L1, Square, Triangle, L1, Square
Mega Password
Pause the game and at the continue/options screen select options and press Triangle, Square, Circle, Square, Triangle, Square, L1, L1 + R1, Select, Select. A skull should confirm the entry. Next, press Triangle, Square, L1, L1, L1, Square, Triangle. You should now have 10 continues, 10 plasma shots and 10 plans You can enter this code as often as you like.