Days after Tirek's near-takeover of Equestria, The Great And Powerful Trixie travels to Ponyville, intent on settling her rivalry with Twilight Sparkle once and for all. No trinkets to fudge her abilities, no megalomania to apologize for -- just pure and simple magician's honor!

Upon her arrival, however, she quickly learns that the information she has on Ponyville -- and Twilight -- is more than a little dated.

Edits (as well as a bit of scene inspiration) courtesy of nanashi_jones.

Her Royal Highness, Princess Luna, is trying to catch up on lost sleep. She deserves it, after all the hard work she's put in to keep the city of Canterlot safe. Now she can turn the lights down, slip into bed, and finally get some rest.

If only Canterlot weren't under attack by the endless swarms of the Changeling army...

Pandinus Imperator (You can call him Pan, he won't mind) is knocked back in time during the Canterlot Invasion, and accidentally kills King Sombra on arrival. Instead of being executed, the changeling is surprised to find himself being hailed as a hero, and is promptly put on the throne as the new monarch, the Crystal Emperor. However, Pan now faces a great many problems, among them Celestia and Luna, who seem certain that the changeling is secretly up to no good, as well as several political factions secretly plotting to undermine his reign. There's also the tiny problem of the constant snowstorm that threatens to cut the city off from the outside world permanently.
The Crystal Ponies need a hero now more than ever before. Why did they get a changeling instead?

We Has A TvTropes.

While not truly a part of Bucking Nonsense's Changeling-Verse, the same rules regarding changeling abilities and society apply.

Cover image provided by gabapple, used with permission.

This story is a sequel to What Have You Done?

Chrysalis, the Changeling Queen, has taken her prize, unhindered by Equestria's precious heroes. Celestia is little more than another prisoner of war now. The Bearers of the Elements of Harmony are lost, and the Elements themselves have turned away from Equestria's plight. As the world they once knew begins to crumble, a single question is asked among the people as they look up at their fallen heroes.

There is no such thing as "miserably ever after," for someone will always be fighting for things to change. Hope doesn't die just because someone's turned off the lights. Truth doesn't vanish when deceit begins its reign, and Harmony can only shine brighter among chaos.
Even as this world falls, we'll work to build it up again.
Even as you lose yourself, you can find greater things within you.
Even as fear rises up like a tidal wave, we'll forge a sanctuary to stand against it.
Even as you break, someone will always be standing there next to you to carry you through it.

Cover art is by Odin-odin.
Story theme (Equestria in Grey) is by Omnipony.
Main Characters are Twilight, Velvet, Discord, Nightlight, Luna, and Chrysalis, in that order.
See you in the comments, my dear readers.

Please do check out the Reading List by Lance Omikron to navigate the Amalgam Universe most clearly

A massive war of titanic forces is taking place in the Kaiju's world. However, when two faction's leaders, the current Godzilla and his 'brother' Xenilla duke it out; humanity unleashes its most devastating weapon. Something beyond comprehension occurred and the boundary that divides worlds, if only for the briefest of moments, was torn to shreds. New forms are taken, new bodies assumed. But old hatreds die hard. But how well can hatreds continue in the world of love and tolerance? Especially with its own demons follow it there?

Godzilla Franchise by Toho Company Ltd.
My Little Pony is owned by Hasbro Studios.
This is a non profit fan-work and I claim no ownership on the IP itself.
Story created by Tarbtano
Co-created and Contributed by Faith-Wolff and Skylark8756

HOLY SHEETZU WE GOT FEATURED! THANKS GUYS!
6/27/2014
Now on TV tropes (Thanks Raidrik, VampyGirl; Lance Omikron, Ultimomant, and ZimFan!)

Kaiju Cast:

Godzilla a.k.a Gojira
Xenilla
Mothra
Anguirus
Rodan
Destroyah

[Character copyright of Toho and Daiei Company, artwork property of Matt Frank]

(for any G-fans, Xenilla is the kaiju you may know as Spacegodzilla. I changed the name because I got quirked about typing it repeatedly and am writing the story so it can at least be understood by just an MLP or just a G-fan; and thought it get very confusing that one character's name was just another character's name with an adjective. Also... don't pretend it's the most imaginative name Toho has every made)

Twilight still isn't having a very good day. An army of changelings is attacking Canterlot, and the experimental spell that blew up in her face has stuck her in a time loop until she gets everything perfect and saves Equestria.

She's got a plan. She's also got a problem: Suddenly, she's not the only one whose day is repeating. And when you're caught between unstoppable force and immovable object, life has a tendency to get complicated.

* * *

This story is an authorized alternate-universe re-imagining of Eakin's Hard Reset, in which multiple loopers turn the time shenanigans up to 11. (Knowledge of Hard Reset is not required, but based on reader comments, will help in sorting out the early chapters.)

Cliff's Notes versions: RampantArcana has started a GitHub repository to codify the time-loop rules and the early-story timeline. Hawthornbunny has posted a chapter-by-chapter breakdown of all the loops, including the ones we don't see, with a lot of critical analysis. Those links contain spoilers (of currently posted chapters). If you're confused, either one of those fan projects is a great starting point, and story comments have a lot of insightful discussion as well.

Publication schedule: 2014 kicked my plot, but as of November I'm picking up the writing again and hope to have something by the end of the month.

Cover art by Alexstrazsa.

Celestia and Luna were born as unassuming foals in troubled times. But already marked for greatness, the simple earth ponies stand to face a world set against them, full of danger, fear, and sadness. A world they will change forever.

A sweeping epic taking place before Equestria was made, where Celestia and Luna must rise from normal foals to become the Princesses we know them as, beset from all sides by monsters, other ponies, and even the forces that govern nature. Their tale is as tragic as it is triumphant.

Currently on hiatus. For more info, go here.

(Cover and internal art by Madmax)
(Editing credit predominantly Lightside Luc)

Twilight isn't having a very good day. An experimental spell blew up in her face, an army of changelings is attacking Canterlot, and she just died. Yet somehow, it looks like it's going to keep going downhill from here.

Given the chance to correct what's gone wrong, Twilight swears she's going to fix all this even if it kills her. Which it will. Frequently.

Cover art by Pixel Prism
Spanish Translation
Series TV Tropes page

After nearly being mugged Twilight turns her considerable talent with magic towards self defense. When a fight with Luna goes farther that either of them wants it to, Twilight will need to find redemption in her new position as Luna's bodyguard and stop a conspiracy that wants to bring back a force more dangerous than either of them.

This story is a sequel to A Stitch in Time

Having discovered the message left for her by Star Swirl the Bearded in the distant past, Twilight once again finds herself caught up in the middle of a struggle against forces far greater than herself. In order to even stand a chance she'll need to travel further and wider than she ever has, and forge some unlikely alliances with old enemies. All to bring down the powers that have manipulated and shaped her entire life, and retake control of her own future.

The conclusion of the Time Loop Trilogy, which began with Hard Reset
Available in Spanish thanks to dgs1993
Series TV Tropes page