Designed by: unknown
Influenced by: Rogue, Nethack, Dragon Quest and others (in theme)
Series: A good number of games; it's hard to easily count how many. Complicating matters is that the series began as, and continues to encourage, cross-overs with other RPG series as part of the main line. There are also "standalone" Mystery Dungeon games in the Shiren the Wanderer line. In the U.S., the most recent games in the series have been Shiren the Wanderer (DS) and the four Pokémon Mystery Dungeon games.
Legacy: Surprisingly extensive. Azure Dreams, Fatal Labyrinth, Time Stalkers/Climax Landers, some aspects of Lufia/Estopolis, Dragon Quest Monsters, Izuna: Legend of the Unemployed Ninja, and still more, none of these could have happened without Mystery Dungeon showing the way.
It's another of those weird little ironies of the game industry that a genre of role-playing games that got its start in U.S. university computer labs would be semi-obscure today, in a Western RPG field that values freedom of action and non-linear quests, while in Japan they'd be a venerable subtype with many games and imitators, while their non-roguelikes have become increasingly linear and abstract. The Mystery Dungeon games, for their excellent 16-bit graphics and relatively detailed quests, are full-on roguelikes that have been sold in retail channels.
The theory I have about the engagingness of roguelikes is that they are a form of random narrative generator. The ups and downs of the player's progress becomes that of the story of the character, who has a relatively plain backstory in order to allow the player to invest more of his own personality into him. Most of these stories end in death, but so do our own, and it makes the few stories that make it to the end even more memorable.
The randomness and difficulty of the game, additionally, help to take responsibility for the failure away from the player. The player knows it's hard so any progress he makes is a sign of valor and heroism, instead of poor decision-making or foolish risk-taking. These kinds of stories aren't made up by a script writer; they come from the player's own actions, so they feel more "real."
Fushigi no Dungeon 2: Fuurai no Shiren
Here's an example of the kinds of strategy the game's random dungeon generator and extensive catalog of possible situations could produce:
In one early area, there is a type of enemy that shoots arrows at the player. the Bowboy. They can fire any time the player is in a direct line. If the player is far away from one and gets shot, he can counter, to some degree, by always moving perpendicular to the route of the arrows.
Unless the Bowboy is close, he'll never be in a direct line, and will have to spend his next turn moving in order to get the player back in line. By continuing to move diagonally towards it, the player can get the monster close enough to whack it with a weapon.
But there are other monsters on these levels. One of them is Snaky -- a tough melee opponent. By themselves the player can usually handle them, but if one is attacking the player and chasing it may add complications to arrow dodging. If the player can maneuver the Snaky between himself and a Bowboy, however, the arrows will strike it, a useful way of getting rid of a foe when in a pinch.
However, when a Bowboy kills another monster with its shots it promotes into a higher-level form, Crossbowboy. They still have the same properties, but their shots are stronger. The player could still handle it, though, if he can dodge its shots in the manner described before.
If a Crossbowboy promotes again it becomes a Mini Tank, a much more dangerous opponent because it gets two turns per round, so it could both move and shoot. If that happens the player probably won't be able to kill or escape it without using some other stuff found in the dungeon, like healing herbs, staff charges, area-effect attack scrolls and many other possible escape items.
What we see here is that the best Mystery Dungeon games do not get their interesting play just from having random dungeons. It's that the random things interact with each other in interesting ways.
Most single enemies are not a big problem on their own, but when several gather at once they are often too much to handle without resorting to items to defeat/escape from them. Or, the player could move carefully to reduce the number of foes he fights at once, or avoid them without even fighting, or use one of a dozen other strategies to survive the encounter.
The game doesn't ensure that all situations are survivable, but it does provide enough random resources to use on each dungeon level that, just from the law of averages, there's usually a way out of the great majority of dangerous situations. Not all the Mystery Dungeon games, it should be noted, are this carefully designed, but when they're on their game, they are some of the most engaging JRPGs ever made.