In NiGHTS into Dreams, Elliot Edwards and Claris Sinclair are the two teenagers who explore Nightopia through their Dreams with NiGHTS. There are seven dreams in total; Spring Valley, Splash Garden, Mystic Forest, Frozen Bell, Soft Museum, Stick Canyon, and a shared dream of Twin Seeds City.
In NiGHTS: Journey of Dreams, William Taylor and Helen Cartwright can access three separate worlds; or Dreams, each created by their Ideyas including one shared dream. Much like NiGHTS into Dreams; there are seven dreams in total: Aqua Garden, Pure Valley, Crystal Castle, Lost Park, Memory Forest, Delight City, and the shared dream of the city Bellbridge.
- In both NiGHTS into Dreams and Journey of Dreams, each Nightopia has an exclusive third level Nightmaren enemy. The reason for that is most likely to make it harder to acquire all of the Mepians.
- In NiGHTS into Dreams, Shleeps only appear in Spring Valley, Mamus only in Splash Garden, Crewle & Pole only in Mystic Forest, Snips only in Frozen Bell, Verols only in Soft Museum and Cuttles only in Stick Canyon.
- In Journey of Dreams, Shleeps only appear in Pure Valley, Baloogas only in Aqua Garden, Scaropions only in Lost Park, Murtles only in Crystal Castle, Mothpils only in Delight City and Deworms only in Memory Forest.
- The word "nightopia" derives from both "night" and "utopia".