use these combos at the character selection screen to enable the indicated effect:
All characters: Right, Left(2), Right, Up(3), Start
Invincibility: Down, Up, Down, Up, Right, Down, Right, Left, Start
Level 99 characters: Up, Down, Up, Down, Left, Up, Left, Right, Start
Add one point to all skills: Left, Right, Left, Right, Down, Up, Start