Invincibility
At the title screen press: A, A, Up, B, B, Down, A, B, Start. When you start the game press pause to become invincible.

Stage Selection
On the ''Press Start'' screen, press L, U, R, D, U, R, L, D, and then one of the following:

U - Stage 2
L - Stage 3
D - Stage 4
R - Stage 5
SELECT - Stage 6
B - Stage 7

View the ending
On the title screen press: A, A, Up, B, B, Down, A, B, B, Start.