Short answers, pulled from the story.
Yuji Horii created the game as scenario director, Akira Toriyama designed the characters and monsters, and Koichi Sugiyama composed the music. These three individuals collaborated on most main series installments until their deaths.
The first Dragon Quest game was released in Japan in 1986. It appeared on the Famicom platform and featured the iconic Slime character designed by Akira Toriyama.
The series was renamed Dragon Warrior to avoid trademark conflicts with an unrelated tabletop role-playing game called DragonQuest. Enix could not use the original name in North America until 2002 when Square Enix registered the Dragon Quest trademark.
The series returned to the name Dragon Quest in North America with the release of Dragon Quest VIII: Journey of the Cursed King in 2005. The first four games had been released under the Dragon Warrior name prior to this date.
Over 300 schoolchildren were arrested for truancy while waiting in stores for the game to be released on the 11th of May 1988. This event led to an urban myth that a law was passed banning the sale of video games except on certain days.
The Dragon Quest music was performed at the opening ceremony of the 2020 Summer Olympics in Tokyo. The series music has been performed annually in concert halls throughout Japan since 1987.