Classic version: Bonus rounds:
Press L, R, L, R, L, R, Right, Select at the title screen in the Classic version. Touch the door that now appears in level 20 to start the bonus rounds.

Classic version: Shoe power-up mode:
Press Select, R, L, Left, Right, R, Select, Right at the title screen in the Classic version.

Classic version: Super Bubble Bobble:
Defeat the Classic version Boss using two players. Then, press Left, R, Left, Select, Left, L, Left, Select in the Classic version.

Classic version: Hidden Coke can item:
Enter I.F as your initials at the high score screen. A sound will confirm correct code entry. A Coke may now appear on floor 1. When collected it will trigger a meteor shower to kill your enemies.