The object of Mr. Do! is to score as many points as possible by digging tunnels through the ground and collecting cherries. The title character, Mr. Do (a circus clown—except for the original Japanese version of the game in which he is a snowman. See flyer image at right of this text), is constantly chased by red monsters resembling small dinosaurs, and the player loses a life if Mr. Do is caught by one. The game is over when the last life is lost.

Cherries are distributed throughout the level in groups of eight. 500 bonus points are awarded if Mr. Do collects eight cherries in a row without stopping. A level is complete when all cherries are removed, all monsters are destroyed, "EXTRA" is spelled, or a diamond is found.

Mr. Do can defeat the monsters by hitting them with his bouncing "power ball" or by dropping large apples on them. While the power ball is bouncing toward a monster, Mr. Do is defenseless. If the ball bounces into an area where there are no monsters to hit (such as behind a fallen apple), Mr. Do cannot use it again until he has retrieved it. When the power ball hits a monster, it then reforms in Mr. Do's hands after a delay that increases with each use.

Mr. Do or the red monsters can push an apple off the edge of a vertical tunnel and crush one or more monsters. If an apple falls more than its own height, it breaks and disappears. Mr. Do can also be crushed by a falling apple causing a loss of life.

Occasionally, the red monsters transform briefly into more powerful multicolored monsters that can tunnel through the ground. If one of these digs through a cherry, it leaves fewer cherries (and fewer points) for Mr. Do to collect. When it digs under an apple, it often crushes itself, other red/blue monsters, and/or Mr. Do.

Each time the score passes a certain threshold during play (5000 points), a letter from the word "EXTRA" appears on the playfield as an Alphamonster, and the player can defeat or be defeated by this monster in the same way as a red monster. Defeating an Alphamonster awards that letter to the player, and collecting all five letters of the word completes the level, plays a cut scene inexplicably playing the theme to Astro Boy, and awards the player an extra life. Alphamonsters attempt to eat any apples they encounter, which makes them difficult (but not impossible) to crush.

The red monsters spawn at the center of the screen. After they have all appeared, the generator will turn into a food item; picking this up scores bonus points, freezes all the red monsters, and calls out an Alphamonster and three large blue monsters. The latter can eat apples as well. The red monsters stay frozen (but still deadly) until the player either defeats all three blue monsters, defeats the Alphamonster (in which case any remaining blue monsters are turned into apples), loses a life, or completes the stage.

Rarely, dropping an apple will reveal a diamond which, if collected within about 15 seconds, completes the level and awards a bonus credit to the player (as well as 8000 points), allowing him or her to play a free game. (This feature is relatively uncommon among arcade video games, though it is a standard feature of many pinball machines.)

Mr. Do!, like many games of its time, has been ported to a variety of computer systems and video game consoles, including the Atari 2600, several Atari 8-bit home computers, the ColecoVision, Apple II, MSX, Tomy Tutor and the Commodore 64 series of computers.  The game has also been adapted to more advanced systems, including Nintendo's Game Boy and Super NES (providing some new gameplay features), and a standalone handheld LCD adaptation was released by Tomy in 1983.  Each port offers varying differences in gameplay from the arcade version, the most common of which is the fact that the bonus credit awarded by the diamond has been removed.  The game has also seen numerous unauthorized clones released for various hardware platforms.

One of the differences in the ColecoVision adaptation is, the alphamonster and sidekicks are unable to eat apples, making them easier to crush, but the blue monsters eat the shrubbery and cherries. Another change is, if an alphamonster is over a letter that has already been defeated, the dinosaur monsters just freeze for a few seconds.

Mr. Do! was followed by three sequels: Mr. Do's Castle in 1983 (also known as Mr. Do vs. the Unicorns), Mr. Do's Wild Ride and Do! Run Run both in 1984.

An expanded 99-level version of Mr. Do! was developed for the arcades by Electrocoin in 1989.

A completely new version of the game, Neo Mr. Do!, was developed by Visco and licensed by Universal for SNK's Neo Geo system in 1996.

A loose rebranded adaptation of the game was released for the Game Boy Color in 1999, titled Quest: Fantasy Challenge. It was developed by Imagineer, and published by Sunsoft. It is branded as a "Quest" series game instead of Mr. Do!

There is also a scheduled release of the arcade version on the Wii Virtual Console released in Japan on April 27, 2010.

On release, Famicom Tsūshin scored the Super Famicom version of the game a 25 out of 40.

• Mr. Do! at the Killer List of Videogames (retrieved February 9, 2005)
• Mr. Do! guide at StrategyWiki
• The Arcade Flyer Archive entry for Mr. Do!
• arcade-history.com entry on Mr. Do! (retrieved February 11, 2005)