Bubble Bobble

Level skip:
Select "Bubble Bobble" mode from the main menu. Immediately press Down, Up, Down, Up, Right, Down, Left, Down, Up Down when the main title screen with the Taito copyright appears. The words "Debug Enabled" will appear in the bottom left corner of the screen to confirm correct code entry. Press R during game play to jump to the next level or L to return to the previous level.

Original version:
Select "Bubble Bobble" mode from the main menu. Immediately press Right, Left, Up, Down, Up, Down, Up when the main title screen with the Taito copyright appears. The words "Original Game" will appear in the lower left corner of the screen to confirm correct code entry. The original version of the game allows you to enter the diamond rooms at levels 20, 30 and 40 even if you lose a life.

Bonus characters:
Start a new puzzle, then press Left(2), Up, Down, L, R, L, R, L + R at the path selection screen.