How would one justify genres, when all are quirky in one manner or another (barring Random, as that's become less an actual genre and more a filler genre as of late)? And furthermore, how is one to destroy such justifications, should they exist in-story?

I'll start with crossovers, as that is one genre I am most familiar with. To justify their presence, one must find elements of another story/game/whatever that meshes well with MLP, and make it work. Sometimes, sadly, one has to cherry-pick if the material doesn't mesh well at all, or do a little worldbuilding to make it happen. Character A from Franchise B isn't going to be enough to cut it in Equestria C after all.

To destroy that justification? Either don't find what meshes well, or give Character A Godmode where it isn't necessary. Or write Displaced, that works too, sadly.

What are your thoughts about this? I'd like to hear them.