These cheats don't work on every release of the game, but give it a try.

Press F1 to advance 1 level
Press F2 to advance six levels
Press F3 to advance eleven levels

TIPS

While in the first screen, bubble the first two monsters and then fill the
screen with hundreds of bubbles. Bubble and burst the remaining monster and
the remaining bubbles should turn into fruit (usually bananas), each of
which is worth 500 points. Also, Hold down after losing your last life, and
you should get another set of lives, though your score will be reset.

If you can get to levels 10, 20, 30 and 40 without losing a life, a magic
door will appear to take you to a bonus screen, and if you can get up to
stage 50 without losing a life, a magic door will appear and take you to
level 70. On levels 7 & 22 wait a few seconds until an umbrella falls and
grab it, you will warp ahead 6 levels. Alternatively, try these:

Beating level 100: jump on the small platforms to collect all the green
potion bottles. They will give you lightning bolts. Straight away fall to
the bottom left hand corner, face in to the corner and fire like hell. The
big guy at the end very rarely goes into the bottom corner, if he does
don't worry just repeat the above process. After 100 hits, he will turn
into a bubble. Pop him and you've done it!