Nightmare Fluttershy.

When training new models and concepts you often experience some level of 'concept bleed' unless you rigorously defend against it with a huge set of regularization images, unfortunately such a set doesn't really exist for pony so generally you just sort of have to accept it and hope whatever you want to learn comes about before too much damage is done.

I however think it's fascinating in cases like this where the parts of the model that began to degrade were more about… I don't know what you'd call it, but 'tone'. The characters visual signifiers are all relatively intact but the model has learned and overwritten 'presentation', 'mood', etc. Obviously the AI doesn't really understand what those things are but it was still able to identify and convey them with almost no damage to the understanding of the character beyond the slit iris of the eyes.

This is also a great example of how AI's are able to generate new works and are not just pixel level photobashers, this is a literal example of the ai learning fluttershy, learning nightmare moon and being able to synergize concepts. Even if you ignore the Nightmareified eyes, you cant deny that the darker 'tone' of the image still is there befitting the Nightmare.