Enter the following codes at the main menu, if you enter the code wrong, press Select to reset the entry process. You will hear a sound upon correct entry.

Effect	Code
Debug Menu, hold select to go anywhere in level	Down, Down, Down, Left, Left, Left, Left, Up, Up, Up.
Immortality and can freeze in mid-air	Right, Right, Right, Right, Left, Left, Left, Right, Right, Up.
Press select to freeze in mid-air	Left, Left, Left, Right, Right, Right, Left, Left, Left, Up.
Unlocks all levels (need a saved game) and can freeze in mid-air	Right, Left, Right, Right, Left, Right, Right, Right, Left, Up.
Unlocks boss levels and can freeze in mid-air	Right, Right, Right, Left, Right, Right, Right, Left, Right, Up.