Similar to the game Dig Dug, Mr. Do! featured an underground digger that had to collect points while avoiding monsters who were trying to destroy him. The title character was a genial circus clown who dug tunnels and went after cherries that represented points. His enemies were red monsters that could be vanquished with a little skill and hard work.

The cherries appeared randomly in solid ground all around Mr. Do. To get them, the clown had to avoid the red monsters who were after him. His one offensive weapon was the "powerball," an explosive device that could be launched at the monsters. Monsters and powerball went boom and the powerball reformed in the hands of Mr. Do, who would be vulnerable until he regained his weapon.

Another way to destroy the monsters was to set traps for them using the heavy, large apples strewn along the playfield among the cherries. By digging at the ground under the apples, Mr. Do could bring them crashing down on the monsters' heads or roll them off a cliff, likewise crashing down on a monster's head. If apples fell too far, they shattered themselves and were of no use anymore.

Very rarely, an apple would be hiding a diamond which could be collected by the player and earn him advancement to the next level and a free game. Diamonds didn't happen very often but oh, it was a happy day at the arcade when your Mr. Do found one.

The more conventional way to get to the next level was to clear the current level of all fruit or killing all the red monsters. A slightly harder way to advance involved spelling the word 'EXTRA' by destroying a special Alphamonster that appeared in the game. Alphamonsters were harder to crush with apples because they could eat right through them but the task wasn't impossible.

Mr. Do! was very popular and gave rise to a number of follow-up games, like Mr. Do's Castle, Mr. Do's Wild Ride and Mr. Do! Vs. Unicorns (for some inexplicable reason).