I hear fanfiction. Rarity gets turned into a dragon because she said some comment about dragons and Spike was hurt. She thinks it will turn him into a baby dragon like him but the spell takes her age and makes it dragon. Then dude turns into a big ass scary dragon Rarity clams him down if you know what I mean and at night you can hear to dragons roaring in the background then the next day they are back to normal and the princess explanes that dragons age in many ways magic greed normal or based on their need so then Spike and Rarity hook up and have a bunch of kirin babys get old and die in each others arms