A few years have passed since Princess Luna was purged of the evil known as Nightmare Moon by the Elements of Harmony. She took back her rightful place on the throne of Equestria at her sisters side.
On a sunny day, a couple of seemingly mundane events trigger memories long forgotten. Memories of a secret Luna hast kept to herself for far too long. Facing Celestia won't be easy. But she has no choice. It is her duty to care for her subjects, and she has to retake the responsibility she could not fulfill while banished to the moon.

In terms of full disclosure, the story got a review by TheifofZ.

What has happened since her disappearance? What will she find? A joyful reunion or devastation? What happened to her Children of the Night?

Inspired by Children of the Night. Cover art is a screenshot from the video. I do not know if there is an "official" story for the Children of the Night and I do not claim mine to be "canon" in the context of the video. These are just my thoughts on what might have happened back in the days.

This story takes place right before the season 4 finale.

Twilight Sparkle uses a teleport spell and goes into the future. It works.

Coverart by: 2snacks

Now has a dramatic reading by Goombasa
Also exists IN SPANISH now thanks to SPANIARD KIWI

Apple Bloom takes a shortcut on a joint project for Twilight time. This poor decision inadvertently leads to a discovery about herself that will change her life forever.

*Contains slight diaper usage*

Twilight Sparkle, as hungry for knowledge as the great unicorn mage Starswirl the Bearded, has created a portal to the multiverse, where endless wisdom awaits her. Excited, proud, and perhaps too tired to be thinking straight, Twilight jumps right into adventure! What does she find? Well, she certainly isn't too big for her britches... compared to the giant horses she meets, how could she be? Suddenly feeling pretty small, Twilight finds herself a foal for a night until she can find a way to prove she's intelligent. Well, it could be worse; at least these Big Horses make some pretty good parents.

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

This story is a sequel to Hard Reset

After the events of Hard Reset Twilight's life and mental well being are slowly returning to normal. Her recovery is cut short, though, when a letter arrives informing her that the time loop spell she cast is causing severe damage to space and time itself. In over her head, Twilight tries to summon anypony who will know how to fix it. The pony she gets is the last one she ever thought she would meet... and nothing like she expected him to be.

Available in Spanish thanks to dgs1993
Series TV Tropes page

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

Rainbow Dash asked Twilight Sparkle out on a date. On the first of April.

When one pony plays a prank, and the other lays out their heart for all to see, disaster is bound to follow. A prank is by definition dishonest, but you don't need to lie to pull a prank.

I hate doing descriptions...
Happy April Fool's day! I felt guilty for not doing a Valentines day special so you get a special for a minor holiday instead!

Cover art generously provided by the wonderful Angelic Flight over on DA. Go check her out!

This story is a sequel to Headless, not Heartless

Okay, taking it from the top.
Hi, I'm Auric Fulcrum, also known as Frank DeFontaine. For about 1,500 years, I wasn't alive. I instead inhabited my Dullahan costume as a spirit because of my sword, which also brought me to Equestria. Once I got here, after a few years of back and forth, Sunbutt imprisoned me because of a minor misunderstanding.
I heard that!
You were meant to!
Anyways, once I got out, I learned that the Wise One was coming to this reality, so I did what came natural to me.
I sought out the power of the Golden Sun and used it to defeat him so utterly I would never have to worry about him again.
Problem was, the energies that bound me together and the power of the Sun conflicted, so my armor fell apart. And without the armor, I was unbound, unfocused.
I came to a week later in the same basement I had been imprisoned, in my old body, but with a few...upgrades. Like Alchemy being a Thing I can Do.
Now that I'm alive again, my to-do list is radically different, but no less daunting.
For starters, how am I supposed to stop a mountain from sinking into the earth?!

"The pieces are set, and the dice are in play. But does every pony have the heart for this day?"

Nearly two hundred years have passed since Rarity Belle merged with the Crystal Heart and took the throne of the Crystal Empire. Since then, through her care, determination, and vision, the Empire has flourished like never before. Now Empress Rarity stands as not a ruler of a providence, but the monarch of a rising superpower.

Today though, is the Empress' Birthday, and Lady Merry Sapphire, seneschal to the Empress, is determined to make this the best birthday Rarity has ever had. Little does she know that not everypony shares her enthusiasm for today...

Notes:
This is an official prequel to the Princess Twilight Sparkle's Birthday stories, created by Autumnschild. This story will develop and expand much of the world we made, but taking place 250 years before PTS500 and its sequel, PTS505. Due to its time gap and status as a prequel, you do not need to read the stories created by Autumnschild, and I have done my best to help that. However, knowing what happened in them will help you be a bit more aware of what is going on, and I encourage you to go read them for they are very enjoyable.

We now have our own group! Come check out the Birthdayverse!

Credit goes to Autumnschild for the proofreading for this story.
Razalon The Lizardman is credited for the grammatical overhaul.

Great thanks goes to these two, for this story would not be as good without them.