Aero the Acro-Bat

Level select:
Press Down, A, Down, Y, Down, A, Down, Y on the options screen. A sound will confirm correct code entry. Begin game play on the first level. Press Start to pause the game when Aero appears. Press Up, X, Down, B, Left, Y, Right, A, L, R. A sound will confirm correct code entry. After game play is resumed, press Start to pause, then press Select. Then hold R while the bonus points are calculated at the end of any level.

Full level select menu:
Enable the "Level select" code. Press L, R, X, B, Left, Up, Right, Down, Y, A at the level select screen. Additional options will appear on the level select menu. Enter the following codes to enable the corresponding options on this menu.

Infinite stars
Press A, Y, L, Up, Down, R, A, Y, Right, Left at the full level select menu. The "Infinite Stars" option may now be selected.

No enemy collision
Press Down, A, Y, R, Y, B, Up, L, Y, A at the full level select menu. The "No enemy collision" option may now be selected.

Infinite lives
Press Up, Down, Up, Down, Left, Right, R, L, Y, A at the full level select menu. The "Infinite Lives" option may now be selected.

Five continues:
Quickly press X, Y, B, A, X, A, B, Y, Up, L at the title picture that features Aero flying. (This is not the title screen.) A sound will confirm correct code entry.

Nine continues:
Press X, Y, B, A, X, A, B, Y, Up, R at the title picture that features Aero flying. (This is not the title screen.) A sound will confirm correct code entry.