Twilight learns an unpleasant fact about being an alicorn: due to the magic in their bodies, they can't use normal toilets and will destroy any bathrooms they try to use. Not only that, the used diapers are processed and filtered and end up as alchemical and even food ingredients. A coronation with an awkward invisible diaper, stealth masturbation in public, and Spike going above and beyond to assist ensues.