Cosmic beings! Creators of worlds! Also, you, me, and that other guy. Simply put, those people who write LNH stories!
Within the story, the Writers are regarded many ways; as godlike (and perfectly worshipable) beings, as blind demiurges, as hard-working sympathetic types, as idiots who should know better. The Looniverse's existence is fueled by the Drama they channel into it. Some say that they are conduits for the unknowable creativity of the Source Code.