My Little Alicorn (EqDaily) is a My Little Pony: Friendship Is MagicFan Fic by InsertAuthorHere. Posted at FIMFiction here.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…Two sequels can be found here and here.
NEVER say that Luna is a traitor, and especially don't call her Nightmare Moon. The Canterlot Nobility can attest to the first, and Celestia learned the second first hoof.
Insulting Rarity around Spike is a bad idea. Try to get her punished for your actions like Blueblood did in chapter 17? He'll Flash Step into your face, looking for all the world like he's going to eat you. Call Spike a monster for that? The only thing keeping Rarity from throttling you is propriety.
Do anything to hurt Twilight, and Shining Armor will make sure you suffer.
Big "NO!": Celestia gives one of these when she realizes that Twilight is about to discover her as a filly. Later, she does this again when Pinkie uses the Anti-Smile Equation to make her realize that she’ll never be a normal pony, even as a filly.
Big "Shut Up!": Kuchen accused Celestia of being an unworthy fraud, and of ruining his and Luna’s lives. She responded with this trope and a Neck Snap.
Bowdlerise: An alternate version of Chapter 15 was posted after some readers found Discord's scene too gory compared to the rest of the fic. Both versions are identical before and after the scene, but any references to pony cannibalism, graphic depictions of Celestia's injuries, and Discord's taunts are removed. Both versions still exist online, however.
Cerebus Syndrome: The early chapters are mostly the silly adventures of Luna, Twilight and a filly Celestia. And then the Kuchen subplot comes along…
Could Have Avoided This Plot: 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 and Kuchen's existence. Turns out Celestia could have done something about that curse if they had just asked her.
Death Glare: Subverted. Lofty tries to use The Stare on Blueblood, but isn't menacing enough to pull it off.
Deconstruction: Of Luna just being welcomed back to Equestria after been freed from Nightmare Moon. Twilight is repeatedly called out for putting so much trust in the mare who, mere weeks before (in story) nearly killed them all, and the citizens are outright terrified of Luna, thinking that one wrong move is all it will take for her to turn on them again.
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.
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.
Dude, Not Funny!: That being said, one of the pranks involved Celestia tricking Luna into thinking she had a fatal disease. She had every right to be pissed after that. Later, Luna decides the joke's over after Twilight calls her out for humiliating Celestia.
Easily Forgiven: After Kuchen (or at least the part of Kuchen in Pinkie's mind) has been shown the magic of friendship in Twilight’s mind, Pinkie decides that five hundred years of floating around in his descendants’ minds is enough punishment for the slaughter of countless ponies.
Entertainingly Wrong: Spike knows something’s up when he receives Twilight’s letter about Celestia’s “absence” and Luna taking her place, since as far as he knows Celestia has never taken a vacation before. So he assumes that Luna has become evil again and enslaved Twilight, which prompts him to bring the other five to Canterlot.
Evilutionary Biologist: Kuchen's ultimate goal was to make himself into an Alicorn by reverse-engineering Nightmare Moon's powers. He managed to kill countless ponies before Celestia finally came by, pointed out the flaws in his research, and snapped his neck.
Eye Scream: Celestia takes a blow to the eye thanks to an incredibly unsafe carnival ride. And that's nothing compared to the time Discord gouged one of her eyes out.
Ignored Epiphany: For the briefest moment, Kuchen realizes that all his work was for nothing, and that he had just committed countless murders, ruined his family, and killed his best friend for nothing. It doesn't last though, killing his Last-Second Chance and ending with his death.
In the Blood: Kuchen cursed his wife and children to have all of his memories, so he could pull a Grand Theft Me after he died. Subverted, in that it didn't exactly take: of his three children, the spell flat-out didn't work on two, and even in the only one that was affected (Pinkie's ancestress), the spell decayed over the centuries to the point where it was just a little voice in Pinkie's head.
Even earlier, Celestia's reaction to the nobles apologizing for their behavior…after she had almost poisoned them all with Poison Joke because of said behavior. She really didn't take it well at all.
Never My Fault: Kuchen murders his former friend Stormwind in cold blood. He later blames this on Celestia, claiming that she “made [him]” do it. While she did bear some responsibility in making him focus strictly on his work, that doesn’t change the fact that he was almost eager to kill ponies in the first place.
Nice Job Breaking It, Hero: Eager for the chance to release Nightmare Moon five hundred years early, Celestia ordered Kuchen to spend all of his time researching at the expense of his family. Needless to say, this backfired spectacularly.
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. It doesn't work. Later Subverted when Celestia actually dyes her coat and hair and wears a dress designed to hide her wings and cutie mark.
Parents as People: Fizzleberry, Orange Peel's father, isn't actually a horrible pony despite his antiquated, brutal views on how one is supposed to raise a foal. He's trying, though.
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.
In the sequel, Cadence's parents sent her to live in Canterlot because she was born an Alicorn.
Porn Stash: Celestia's Royal Porn Collection. It actually belonged to Twilight's mom.
Sequel Hook: At the end of the story, Blueblood is still a colt, and is sentenced to Magic Kindergarten. Celestia is normal, but still has one of the toys from before, and has some (small) lingering reservations about going back.Word of God is that both hooks have their own fics planned.
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. Just looking at it is enough to creep Twilight out.
Too Dumb to Live: Blueblood actually goes so far as to try and blackmail Luna to support his revenge schemes. He gets placed under house arrest for his troubles, right after Luna shows him why angering a God Princess is a bad idea.
He tries a second time in the last two chapters, including breaking into the palace and disrupting a dangerous ritual. He's very lucky he only got flung out a window, chibified, dropped from ceiling height by Rainbow Dash and left as a foal, rather than say, sent to the moon, actually hurt by the drop, been beaten by a Mama Bear, or incinerated by Spike for insulting Rarity and demanding she be punished for the Gala fiasco.
Time Abyss: Celestia predates macroscopic life in Equestria. Luna isn't quite as old, but was an adult before anypony other than Celestia existed.
What the Hell, Hero?: When the rest of the Mane Six realize that Twilight both knew about Luna cursing Celestia, and actually sided with Luna in the matter, they are not happy. Pinkie in particular is completely outraged, mainly because she has a personal history with the curse.
Who's Laughing Now?: A minor version of this is what sets off the story-after Celestia goes too far with her pranking, Luna decides to return some of the indignities she's suffered at her big sister's hooves by making her the little sister for a while.
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."
Twilight: "What's a tattoo scrubber?"
Octavia: "It's best that you don't know. Believe me, I wish I still did not."