Mario is Missing is one of Nintendo's many entries into the "edutainment" genre, and one of the few Nintendo games to feature the Mario brother Luigi as the main playable character.
Mario is Missing is a unique Mario game in that the action does not occur in the Mushroom Kingdom, but rather on terrestrial Earth, set in a time contemporary to the game's release date. The visual style of the game is borrowed its SNES contemporary Super Mario World, from the title's font to the overworld city maps.
Mario sets off towards Bowser's castle to stop Bowser's evil plan of covering the world in water by melting Antarctica. It is later discovered that Bowser plans to melt the continent with a large number of hair dryers, purchased with money gained from stolen valuable artifacts from across the Earth.
While Luigi is hesitant to enter Bowser's castle, Mario makes a bold entrance, only to be captured moments later. Luigi must then enter the castle solo, searching through each of the dungeon's warp doors for Mario, while at the same time recovering all of the stolen artifacts from Bowser's loyal Koopas. Upon returning each stolen artifact, more doors to the castle unlock, allowing Luigi to search more places until he eventually reaches Antarctica to save his brother and stop Bowser from his evil plan.
From the warp doors in Bowser's castle, players are transported to various cities across the world. Here, by the flyers attached to tourist information booths, Luigi discovers that the Koopas have stolen culturally significant artifacts. Luigi is able to speak to other people populating the town, ranging from a professor, to a schoolboy, to a police woman. The player gathers clues to correctly identify the missing artifacts, such as the Sistine Chapel painting, or the Forbidden City. To gather additional clues, Luigi also has access to a computer and telephone, both from which he can learn about the missing artifacts. Luigi can call general information, and also receives calls from Mario from time to time, giving tips on generic gameplay.
Players also have access to an overworld map, showing the street connections, as well as Koopa and warp pipe locations. Being in the real world, Luigi is also able to speed up travel by taking a taxi cab across town, or out to hard to reach places, such as Alcatraz Island.
A map showing the entire world, called the Globulator, allows players to control Yoshi, as he hops from continent to continent. When the player places Yoshi on the correct city of Luigi's location, Yoshi appears on the stage with him, and Luigi is able to ride the dinosaur throughout the city. Players will not be able to stomp on Koopas until they have acquired Yoshi.
Once the player has stomped a Koopa to reclaim an artifact, Luigi must take it back to the proper information booth. There, the player will be asked a series of questions by an information attendant, bearing resemblance to Princess Peach. If the player fails a certain number of questions, she will dismiss Luigi as a phony, and he will have to wait until the information booth is reopened to attempt to return the artifact again.
Upon the successful returning and delivery, Luigi takes a picture of the fully restored artifact for his photo album. Players are able to view this photo album at any point in the game, along with the facts learned along the way about the important cultural piece.