Access Bonus levels:
At the classic mode title screen, press L, R, L, R, L, R, Right, Select. Level 20 will now have a door in it. Touch it go start the bonus rounds.
Powerop mode:
At the classic mode title screen, press Select, R, L ,Left , Right, R, Select, Right.
Super Bubble Bobble:
To unlock the a harder difficulty in classic mode, you first must beat the last boss using 2 players. Then at the classic mode title screen, press Left, R, Left, Select, Left, L, Left, Select to unlock the harder version.
Unlock Robolun:
Beat all 100 levels in the new version of the game, and he should appear at the character select screen. He's faster, but can't jump as high.
Unlock Lovelun:
Using Robolun, beat all 100 levels in the new version of the game again. This will unlock Lovelun, who shoots bubbles farther and faster than normal.
