A Human turned pony hybrid finds himself in Equestria, when he sees what Discord's doing to the world he realises that the world is now like a cartoon. Taking that logic a step further, if the 'Normal' rules of Magic and Science don't apply, then could anyone shape the world to their Will, seeing as the rules that would normally stop them aren't working.
After a quick experiment, the Human seeks the assistance of the one pony with experience in shaping the fabric of reality, Princess Luna.
Together they conspire to derail Discord's plans.