A troubled Princess Celestia, wandering her School for Gifted Unicorns late one night, chances upon her young faithful student Twilight Sparkle, who has problems of her own:

She can't catch the Tooth Flutterpony.

What possible advice could Princess Celestia give to her upset young pupil, who is desperately trying to prove that an old ponies' tale is real?

Inspired by Skywriter's How to Remove a Unicorn Tooth (which is a much better story and you should probably go read it, if you already haven't); and, of course, Sir Terry Pratchett's Hogfather (which you should have already read, and even if you have, you should go read it again).