Nine continues:
Quickly enter this sequence when you see Aero flying before the game starts:
X, Y, B, A, X, A, B, Y, Up, R
Level select (needed for other cheats below):
This is a bit complicated and requires a few steps, but chill! We'll break it down for ya! ...
1) At the options screen enter this code: Down, A, Down, Y, Down, A, Down.
A sound will confirm correct code entry.
2) Start playing the game and then pause the game when Aero appears and enter this sequence:
Up, X, Down, B, Left, Y, Right, A, L, R.
A sound will confirm correct code entry.
3) The game will restart from where you left off, then pause the game again and press select.
4) Now hold R while the bonus points are calculated at the end of any level. Extended level select (needed for other cheats below):
1) Do the level select code above.
2) Enter this sequence at the level select screen:
L, R, X, B, Left, Up, Right, Down, Y, A
This will give you some extras to play the game.
After you have done the two level select cheats you can then do a couple more, but they will only work if you do the two level select cheats first.
You enter any of the following codes at the extended level select screen.
Infinite stars
A, Y, L, Up, Down, R, A, Y, Right, Left.
No enemy collision
A, Y, R, Y, B, Up, L, Y, A.