Rainbow Dash promised her stepdaughter, Scootaloo to get her a Zapp action figure for Hearth's Warming. However, the toy is sold out at every single store, resorting her to travel all over Equestria to find one.
Finding the perfect Hearth's Warming present for someone you barely know is hard. That's doubly true when you're Star Tracker, and the pony you're buying for is Princess Twilight.
For generosity's sake, Rarity reluctantly fulfils Derpy's odd request. But in the world of fashion, no good deed goes unpunished. (Impossible Numbers' entry for The Obselescence Memorial Jinglemas Twinglemas Secret Santa Sendoff: Part 2 Edition!)