A simple accident with magic results in a pony claiming to be an accountant appearing on Twilight Sparkle's door-step, and that is just the beginning of an epic tale of revenge, laughter, chaos, family, petty squabbles and on a few occasions, true love, spread across time, space, and entire universes.
Well, sort of.

First time writing. Constructive criticism welcome.

Now has a TVTropes page

While visiting Canterlot with Limestone, Marble runs into an energetic pony who could match her twin in cheerfulness. And she's cute. And wants to talk to her. And cute.

Naturally, Marble explodes from shyness.

Pre-read by: Timaeus
Ch. 1 Audio Reading by TheCaptainSand - Scarlett Blade

A.K. Yearly's epic continuation of Daring Do is coming up. While fans eagerly await the next installment of the series, Yearly's publishers eagerly anticipate the estimated profit.

So what happens when they find out everything was real?

Picture by Austiniousi

Nightmare Moon had finally broken free of her prison. It was time to get her revenge on Celestia and bring about night eternal. Six mortal ponies rose up to stop her, using the power of the Elements of Harmony.

When the dust had cleared Nightmare Moon was gone, but so was Luna.

Be warned, there may be spoilers in the comments.

Princess Twilight Sparkle discovers a centuries-old mystery hidden in the Royal Archives. Her investigation leads through layer after layer of deception and misdirection, setting her hooves on a path that seems to be leading to a mysterious secret. Along the way, she learns that some friendships can be very, very strange.

Book 1 of the Alicorn Adventure series.

AUDIOBOOK by VisualPony
Featured at the Royal Canterlot Library
TV Tropes Page (Courtesy of Sandtalon)
Goodreads Page (Courtesy of Facedeer)
Equestria Daily Page

WARNING: Major spoilers in the comments. Takes place several months after the end of season four. (Not a Da Vinci Code crossover, BTW!)

Do you see a dark tag? No, you don't. Not dark. Well, okay, there are a couple of dark-ish bits, but that's all. Not enough to warrant a tag. Speaking of tags, there really ought to be "Badass Twilight" and "Friendshipping" ones.

Sequels and side-stories (and more) can be found here Offprint and AO3, and a hardbound two-volume set of all that can be ordered from The Ministry of Image.

My editor for the first edition of this story was Gogito, and I can't thank him enough for all the hard work he did. My editor for the revised version was PresentPerfect, and he did a terrific job of getting the story into excellent shape.

Dear Princess Celestia,

First, allow me to offer my deepest apologies.  I have no doubt the news I'm writing to you about has, somehow, already reached you.

Still I know it is my responsibility duty to bring this matter to your attention myself.  Especially given that it involves a national hero.

On my authority as your personal student, I have placed the human known as Gary Stu under citizen's arrest.

Please believe that nopony is more shocked than I am about this.

This story is a sequel to Lyra's Human

Several years after the events of Lyra's Human, Derpy Hooves decides that she's lonely, and wants to meet a human for herself. Together, Derpy and the human have crazy adventures across worlds as both learn what it means to be true friends.

Story image courtesy Shadow Squirrel