Ponyville has been the center of many a strange event the past years. Discord, giant vines, Tirek, an Ursa Minor, and just recently, Cozy Glow's draining Equestria of magic. After all this bad stuff, it makes sense for one or two good events to pop up.
Hearth's Warming preparations are underway when such good event comes with letters to close friends and family with hopes of being loved again.