Sepia Tock is an artisan, friend, and citizen of Ponyville. He is not, however, Doctor Whoof.
This is his story

Queen Chrysalis, ruler of the Changeling Hives, feels a disturbance. Something unusual, something evil... something festive. It doesn't take her long to discover that the source of this dread is a pony holiday by the name of "Hearth's Warming Eve," and it takes even less time for her to decide what she has to do now: She must steal it.

Yes. The whole thing.