The object is to clear each level of cherries and/or monsters. You may kill the monsters by hitting them with your powerball (which bounces through the paths, taking unpredictable directions at junctions) or dropping an apple onto them. The level is also over if you complete the EXTRA box or collect the diamond which appears very infrequently ('Special', awards an extra credit).
You can dig extra paths through the solid parts of the maze in whatever shape you like. The apples will be found dotted around the screen in the solid parts. To construct traps for monsters, you must dig just under them so they fall into the path behind Mr. Do, then turn around and push the apple back to a path which turns downward, preferably just over the edge, and you have a trap! Wait for a monster (or a few) to appear in the path below, and push! If the monsters wait too long under the apple, they can become 'diggers' and dig away at the maze toward you! Sometimes they go under the apple and squash themselves. An improvement is if two apples can be lined up, so you are protected against a 'digger'. You can also dig up to an apple, wait for the monsters to follow you, then move aside and drop it before they can get out of the way.
The central target, from which the monsters appear, may be collected once all the monsters have appeared. This is noticed when it becomes a 'prize', (e.g., ice cream, biscuits, etc.). When you collect the prize, the Alphamonster and his four henchmen appear. The Alphamonster may be in the EXTRA box at the top or moving around the screen. The Alphamonster and his henchmen cannot easily be crushed under apples because they usually eat the apples! They can be killed individually with the powerball or, if the Alphamonster is killed, all the henchmen turn into apples.
This game had three sequels, Mr. Do!'s Castle (1983, also known in Japan as Mr. Do! vs. Unicorns), Mr. Do!'s Wild Ride (1984) and Do! Run Run (1984). All of them had vastly different gameplay styles with Do! Run Run being the most similar to the original's gameplay. Similar games were Fruity Frank on the Amstrad CPC and Digger on the IBM PC.
- Amusement Park: The setting for Wild Ride.
- Artificial Brilliance:
- Nearly every enemy in the series are quick and ruthless hunters that will chase you down at every opportunity.
- In the original game and Run Run, the Alphamonsters will hunt you like any enemy if Mr. Do isn't holding his Power Ball, and will back off if he does.
- Artificial Stupidity: The monsters in the first game aren't very good at dealing with the apples, mostly running back and fourth in an attempt to dodge them.
- Beware the Silly Ones: Mr. Do may be a clown, but he's perfectly capable of killing monsters.
- Dolled-Up Installment: Both Castle and Wild Ride were originally two games unrelated to Mr. Do! known as Knights vs. Unicorns and Go! Go! Coaster respectively. During development, they decided to add in the famous clown, completely turning both the original games into Vaporware.
- Drop The Hammer: Mr. Do wields a wooden hammer in Castle, though it is only useful for knocking out blocks and can only knock the Unicorns back a short distance. Only when they're turned into Alphamonsters via collecting the Shield can Mr. Do directly kill them using the hammer.
- Edible Collectible: There are cherries that can be eaten for points. They are laid out in batches of eight- collect all eight cherries in sequence and you're rewarded with 500 additional points. In Do! Run Run, you can run laps around patches of pellets to convert them into fruits of increasing value.
- End-Game Results Screen: After every scene that ends in a 3, 6, and 9 in the original game, the game displays your score for each level, and the completion time in minutes and seconds. After a scene that ends in 0, it plays a different result screen that always shows your average score/time for each level.
- Endless Game: Every installment except for Neo, though the patterns of stages repeat after a particular scene:
- In the original, the layouts of the levels repeat starting from Scene 11, and the colors of the dirt the player digs through repeat starting from Scene 31.
- In Castle, the castle layouts are reset after Scene 8 while the colors of the stages go in the pattern Green, Magenta, Orange, and Blue.
- In Wild Ride, Scene 7 is identical to Scene 1, Scene 8 is identical to Scene 2, and so on. To increase the difficulty, several additional hazards are added on the second loop.
- In Run Run, all the scenes repeat after Scene 10.
- Family-Unfriendly Death: Do! Run Run's death animation. Mr. Do collapses onto his back and is electrocuted out of nowhere, leaving only his burnt skeleton. Thankfully it's not present in the Japanese version (Super Pierrot).
- Fast Tunnelling: In the first game. Neo Mr. Do also features it, but since the game is played from a top-down perspective with the floor as dirt it resembles kicking away the sand as opposed to plowing through it with Mr. Do's hands. The mobile recreation of Mr. Do! instead has Mr. Do plowing through fields of tall grass and wheat.
- Gender Bender: Neo Mr. Do! has a powerup that turns the title character into a woman, marked with a female symbol.
- Hoist by His Own Petard:
- As in Dig Dug, Mr. Do can wind up crushing himself under the apples laid out underground.
- In Do! Run Run, you can also fall victim to your own rolling logs.
- Nintendo Hard: All the games exhibit this due to being arcade games, though the original game is slightly easier than the three games that followed.
- No Name Given: The only named monsters in the series are the Unicorns from Mr. Do's Castle and the Alpha Monsters.
- Non-Ironic Clown: The title character himself.
- Public Domain Soundtrack: In the first game, the main theme that plays throughout is taken from "The Cancan Song" by Jacques Offenbach, while every three levels, Ludwig van Beethoven's "Turkish March" from The Ruins of Athens (better known to Mexicans as the theme song to El Chavo del ocho) plays for an intermission scene. Averted with the Game Boy version, which uses an original soundtrack.
- Spelling Bonus: Spelling the word E-X-T-R-A by hitting the Alpha Monsters with those letters (or in Wild Ride's case, just collecting the letters before they vanish) earns you an extra life.
- Songs in the Key of Panic: In the first game, if a Monster spots Mr. Do, the music will speed up as the Monster(s) swiftly pursue(s) the player.
- Time Stands Still:
- Collecting the bonus food item in the center of the play field after all the Monsters depart in the original game, and said Monsters will suddenly freeze in their tracks, releasing the Alphamonster (unless it is already out on the prowl) and three Munchers.
- Do! Run Run causes a similar effect, but it only slows the two main monsters instead of completely stopping them.
- Tunnel King: Mr. Do, at least in the first game.
- Turns Red: All of the series' monsters, except for the Alpha Monsters and the ghosts they release, are capable of transformation. In the first game, the red monsters could turn blue to tunnel through dirt (with said action being used more often on higher levels or if the player stalls for too long in the current stage). In Castle, the Unicorn's final evolutionary stage gives it faster/smarter movement and eventually the ability to multiply, which seems to also be the case for the two monster types in Run Run, except less rare and lacking the ability to multiply.
- Underground Level: The first game is set entirely in one. Averted in Namco's mobile remake, where the game instead takes place in the fields of tall grass next to a nearby carnival (after all, Namco had already done its own game about digging undeground).