Invasion From Beyond Cheats
PS1 | Submitted by GamesRadarGet all upgrades, ships and weapons
When you see the PRESS START screen, press L1, R1, L2, R2, Up, Down, Right, Left, Left, Right, Down, Up.
PS1 | Submitted by GamesRadarLevel select
When you see the PRESS START screen, press L1, R1, L2, R2, Triangle, X, Circle, Square, Square, Circle, X, Triangle. Go back to the Start Mission screen and you can pick all the game levels