255 Lives Tricks : It's possible to win 255 lives on the first screen, but only if an apple appears in the top two rows of the playfield.
1) Begin by digging a tunnel directly from the bottom of the screen to just below the apple, but leave enough dirt under it that it doesn't fall.
2) Next, kill all of the enemies but one, then lose all of your extra lives. As soon as you're on your last life, go right under the apple and wait.
3) Eventually, the remaining enemy will come after you. Allow the apple to drop, but, in the interval before you're squashed, kill the enemy with the powerball. If all has gone well, you'll be carried to the bottom of the screen, the music will go haywire for a moment, and you'll be awarded 255 extra lives.
4) Note that you should always lose a life before spelling 'EXTRA', or you'll roll back to zero lives, so, to be safe, immediately kill yourself at the start of level two.
5) IMPORTANT : This trick will only work with the Taito version of Mr. Do!.
Here's A Neat Trick : You can divide the screen into a grid. The cherries, apples, and tunnel corners are all centered on a grid element. If you are being chased by the normal badguys (not ghosts) you can dig and stop between grid elements. The badguy will think it needs to turn into a digger to get you. While he's changing forms, you can escape.
An Alphamonster will appear every time your score reaches a multiple of 5000.