A particularly stubborn human is lost in Equestria and is trying his damnedest to find a way out, while surviving the surprisingly difficult rigours of life in a land filled with cute talking animals. Hilarity ensues.
A human soul is stuffed into King Sombra's body. Having no idea what's going on, and thinking he is in some kind of coma, he just casually strolls into the Crystal Empire.
After the events of A Canterlot Wedding, Queen Chrysalis finds herself in an alien form, in an alien world. Stripped of her powers and at the mercy of one of the locals, she soon learns there is more to life than conquest and domination.