The Singletons are the underlings of NxOgre, not the bad underlings kind, the good ones really. Well, almost. There are five singletons; although the isn’t fifth not shown (He joined us in season 3, and I couldn’t find a more recent screengrab).

They are; ErrorStream, TimeController, ResourceSystem, MeshManager and HeightFieldManager. I’ll let you guess who’s the one in pink.
Although they are the underlings of the World, they can be created before the world, and after the world has perished – If your evil bidding desires it.
World::precreateSingletons();
World* mWorld* = World::createWorld();
World::destroyWorld(false);
World::destroySingletons();
Singletons can be accessed any where, and there is only one of their kind – sadly.
ErrorStream::getSingleton()->throwAssertion("I've broken it!!!", __FILE__, __LINE__);