Press: X, Left, Right, X, on the title screen to unlock Bubble Bobble backgrounds.
On the title screen press X, Left, Right, X. There will be new levels in '1 Player Puzzle mode'.
Set your Saturn's internal clock to any date in Dece,ber to have a Christmas theme. Set it to December 31st or January 1st for a Happy new year theme.
Start a new puzzle and at the screen where you choose your path, press left, Left, Up, Down, L, R, L, R, simultaneously press L and R.