I would say there isnt one but Krag said that so Ill just think in a way that you mean "something fun/amusing" which in that case....
The animê worlds and this world slams together. Thus all antagonist and protagonists of all animes (even the shoju slice of lifes) are all in one world.
An interesting question.I have thought of several versions of how this world could end.One of them would be the war that will break out between the Cosmos opposing forces...