"Mystery Dungeon (不思議のダンジョン, Fushigi no Dungeon) is a series of roguelike video games, most of which were developed by Chunsoft, but with select titles in the series developed by other companies with permission from Chunsoft to use the name.
Although all games in the series bear the Fushigi no Dungeon moniker somewhere in their Japanese titles, only the Shiren the Wanderer games contain original characters; all other license their characters from other role-playing game franchises.
The first title, Torneko no Daibōken: Fushigi no Dungeon starred Torneko, a shopkeeper character from the same developer's Dragon Quest IV (Chunsoft being developer of the first five games Dragon Quest series).
Mystery Dungeon games are notable for being among the few console games in the roguelike genre. The series has inspired similar titles in Japan, most of which appropriate their games mechanics from Mystery Dungeon, rather than Rogue itself."
Source: Wikipedia, "Mystery_Dungeon", available under the CC-BY-SA License.