Hidden Invasion
Easy Mode:
At the title screen, press UP, DOWN(x2), UP, LEFT(x2), UP, RIGHT(x2), UP(x3). A sound will confirm correct code entry.
Big head mode:
Quickly press LEFT(x2), UP(x2), RIGHT(x2), DOWN(x2) at the title screen.
A sound will confirm correct code entry.
Boogie Mode:
At the title screen, press RIGHT, DOWN, LEFT, UP, RIGHT, DOWN, LEFT, UP, RIGHT, DOWN, LEFT, UP, RIGHT, DOWN, LEFT, UP.