Not to be confused with the regular Nightopians.
When attacked by NiGHTS, the Nightmarens throughout the levels will turn into orbs and if the orbs collide with a Nightopian, the latter will lay an egg which contains a Mepian, a Nightopian with body parts of the Nightmaren that collided with the Nightopian.
A Mepian can be born with one to four Nightmaren body parts. These are the Nightmaren head, torso (wings come with it), arms and legs. Hitting a Mepian with a different Nighmaren will make another Mepian, that will have parts of both the hitten Mepian and the Nightmaren used.
Much like the regular Nightopians, NiGHTS behavior will affect the Mepians mood, so they may befriend or hate NiGHTS, depending on the player's action. Unlike the regular Nightopians though, who always care about others of their kind, a Mepian may be nice or may be mean towards regular Nightopians and other Mepians. Some Mepians can be aggressive towards other Nightopians and other Mepians but at the same time, they can befriend NiGHTS.
The Mepians behavior will also affect the Nightopians mood, so if Mepians are mean towards them, the Nightopians' mood will get lower. Much like a regular Nightopian, the Mepians are Nightmarens prey. They also disappear after a while.
- According to the NiGHTS into Dreams Japanese website, the Mepians like to mate and will try to mate with Nightopians against their will.
- In NiGHTS into Dreams, some Mepians' pupil will shrink when either NiGHTS or the visitors come close to them.
- In NiGHTS into Dreams, the Kircle Mepian's torso comes with regular Nightopian wings, making it the only Mepian in the game to keep a Nightopian body part.
- In Journey of Dreams, all of the Mepians will keep the Nightopian's halos when they get the Nightmaren's head.
- The Shleep Mepian is the only Mepian who has appeared in every NiGHTS game.
- The Mepians are one of the nine NiGHTS characters who have appeared in every NiGHTS game, the others are NiGHTS, Reala, Wizeman, Nightopians, Elliot, Claris, the King Pian, and Shleeps.