Enter the code at the ''Classic'' mode's title screen - L, R, L, R, L, R, Right, Select. Level 20 will have a door appear. Touch it, to enter the bonus round.
Power Up! Mode (Classic Version):
At the ''Classic'' Mode title screen enter: Select, R, L, Left, Right, R, Select, Right. This is the same effect as collecting shoes (Move faster, make bubbles faster)
Super Bubble Bobble (Classic Version):
Firstly, beat boss in classic mode with 2 players. Enter code at ''Classic'' mode title screen: Left, R, Left, Select, Left, L, Left, Select. This unlocks the harder mode of the game.
Unlock Robolun (New version):
To unlock Robolun, finish all 100 levels in the new version, and select him from the character select menu. He moves faster than Bobblun and Bubblun, but can't jump as high.
Unlockables:
Unlock Lovelun (New Version)
Complete the new version with Robolun to unlock the final secret character, Lovelun. She can fire bubbles faster and further than the other three characters.
