My Little Alicorn

My Little Alicorn is a My Little Pony Friendship Is Magic Fanfic by InsertAuthorHere.

After getting trolled by Celestia one too many times, Luna decides to have some revenge. She steals the Arcanus E Draconus, the most forbidden spellbook in Equestrian history, and uses one of its spells to age regress Celestia into a foal. To make things even more humiliating, she invites Twilight Sparkle over to unwittingly share in her teacher’s torment.

Then Luna finds out she can’t reverse the spell.

Now Celestia is stuck as a small, powerless filly, while Luna has found herself catapulted into ruling Equestria both day and night. And while all that is going on, Twilight works to find a way to bring Celestia back to normal, only to discover a deeper secret connecting the spell's creator with one of her friends. And then there's Blueblood's schemes to get revenge for that Grand Galloping Gala incident...

A sequel is currently being posted.

This fan fic contains examples of:
"Twilight: "What's a tattoo scrubber?"
 * Zero Percent Approval Rating: Luna, much to her chagrin.
 * A Glass in The Hand: Chapter 12 has a telekinetic variation with Luna
 * Adorkable: Filly Celestia.
 * Awesome McCoolname: Celestia names a pair of toys Lady Pinkinstuff and General Smashemup.
 * Battle in The Center of The Mind: In Chapters 13 and 14, between
 * Berserk Button: NEVER say that Luna is a traitor, and especially don't call her Nightmare Moon. The Canterlot Nobility can attest to the first,
 * Insulting Rarity around Spike is a bad idea.
 * Bowdlerise: An alternate version of Chapter 15 was posted after some readers found  too gory compared to the rest of the fic. Both versions are identical before and after the scene,   Both versions still exist online, however.
 * Bratty Half Pint: Filly Celestia, at times.
 * Brought Down to Normal: As a filly, Celestia is too young to fly and can't use any magic. It makes things more than a little difficult.
 * Cerebus Syndrome: The early chapters are mostly the silly adventures of Luna, Twilight and a filly Celestia. And then the Kuchen subplot comes along...
 * Completely Missing the Point: Spike immediately ignores the obvious intent of Twilight’s letter in favor of a non-existent secret message.
 * Death Glare: Subverted.
 * Deliberately Cute Child: It doesn't exactly take long for Celestia to realize the advantages of being a filly; namely, it makes it a lot easier to manipulate other ponies.
 * Destination Defenestration:
 * Disproportionate Retribution: Runs all over in this fic. Celestia pranks Luna a few too many times, so she turns her into a filly and humiliates her in front of her own student. Blueblood, meanwhile, wants to raze an entire town because a few of its residents ruined the Grand Galloping Gala.
 * Evilutionary Biologist: Kuchen's ultimate goal was to make himself into an Alicorn  He managed to kill countless ponies before Celestia finally came by,   and snapped his neck.
 * Eye Scream: Celestia takes a blow to the eye thanks to an incredibly unsafe carnival ride.
 * Fake-Out Opening: The first chapter treats everything like a very straight Revenge Fic…only for the last line to reveal it was a joke.
 * Fountain of Youth: Happens to Celestia, obviously.
 * And in Chapter 16,
 * From Nobody to Nightmare:
 * Has Two Mommies: Invoked by Celestia in Chapter 3 of the sequel, after she asks Luna to assist her in raising  Luna quickly asks her to call it something else.
 * Humiliation Conga: Luna’s first daytime court does not go well.
 * Handicapped Badass: Celestia never fully recovered from the injuries Discord inflicted when they fought. She's still absurdly powerful.
 * Hulk Speak: How the ancient pony tribes spoke in one flashback. Luna was not impressed.
 * Ignored Epiphany:
 * In the Blood:
 * It Got Worse: What started as a prank quickly snowballs out of control.
 * My God, What Have I Done?: Luna's response to
 * Even earlier,
 * Paper-Thin Disguise: When Celestia first meets Lofty, she doesn't even bother hiding her wings and horn. Instead, she just tries to pass herself off as a visiting relative who happens to look suspiciously like Princess Celestia.  Later Subverted when Celestia actually dyes her coat and hair and wears a dress designed to hide her wings and cutie mark.
 * Parental Neglect: Luna and Celestia's parents dumped them on a lifeless planet as foals and told them to 'make something of themselves'. Luna at least only got dumped after there was macroscopic life.
 * Porn Stash: Celestia's Royal Porn Collection.
 * Raise Him Right This Time: The plot of the sequel.
 * Secret Art:
 * Sequel Hook:  Word of God is that both hooks have their own fics planned.
 * "The Reason You Suck" Speech: Luna gives a particularly effective one to the nobles after they treat her like crap one time too many.
 * Tome of Eldritch Lore: The Arcanus E Draconus. It's printed on dragon skin, the writing is in griffon blood, and it's bound together with glue made from ponies.
 * Too Dumb to Live: Blueblood actually goes so far as to try and blackmail Luna to support his revenge schemes.
 * Time Abyss: Celestia predates macroscopic life in Equestria. Luna isn't quite as old, but was an adult before anypony other than Celestia existed.
 * The Mind Is a Plaything of The Body: Played with. Celestia’s adult memories and personality are all still with her, but also compete with her younger mindset.
 * Unperson: After his death, any and all records of Kuchen's existence are destroyed or suppressed.
 * We Could Have Avoided All This: For generations, the Pie Clan has hidden their true heritage from Celestia, seeing as how the vengeful tyrant will gladly kill them to erase any mention of their  existence.
 * You Do NOT Want to Know: A minor example when Octavia is explaining to Twilight the history of the Pie Clan, and how upon leaving Canterlot 500 years ago they "branched off into all sorts of bizarre professions, from professional mud slingers to tattoo scrubbers."
 * You Do NOT Want to Know: A minor example when Octavia is explaining to Twilight the history of the Pie Clan, and how upon leaving Canterlot 500 years ago they "branched off into all sorts of bizarre professions, from professional mud slingers to tattoo scrubbers."

Octavia: "It's best that you don't know. Believe me, I wish I still did not.""