To commemorate the imprisoning of Discord one year ago, the first annual Celebration of Harmony is starting off with a grand party in Canterlot, something Twilight Sparkle has been looking forward to after many sleepless nights plagued by nightmares. After a chance glance at the party, Twilight and Princess Luna rekindle their friendship sparked on Nightmare Night. Meanwhile, Princess Celestia grows worried over the state of her kingdom, her sister disappearing at odd times, and the seal placed on Discord. Are the princess's worries well founded or is her sister's oddly secretive behavior taking a toll on her nerves? Twilight gets caught between the sun and moon as both royal ponies reveal that there is much that history has forgotten about the nature of the alicorns and even the draconequus.

AU for not taking into account Season 3 canon.

Amazing cover art by Sai, check the image source for more of his great work!

Twilight Sparkle wakes up one morning to find she's undergone some changes. She shortly discovers she wasn't the only one. (New cover art by Jamey4 on deviantart http://jamey4.deviantart.com/)

Warning, this work of fiction contains multiple fourth wall breaks, massive silliness, and more than a trace amount of alicorns.
The author may or may not have snapped at times in the writing of this work, and it shows. Bring a towel, you may get wet.

Princess Luna's Lunar Stallions are an elite guard force of seventy, the descendants of the originals from a thousand years ago. Her lover leads them, and they've begun to flourish and be accepted by society. But now there's a new super-power in Canterlot, and she's killing the criminal ponies she catches rather than arresting them. The descendant of Luna's avatar of WAR has emerged. Her ancestor was the one mare to ever go into battle with the Lunar Stallions, the Moon Champion. Can the Lunar Stallions stop this killing machine? Who is she?

Luna is on her way to visit Celestia, but hears her squealing for someone to 'stop!'

She walks in on Twilight on top of a red-faced Celestia, and the two of them react like guilty teenagers. Just what the buck is going on here?!

Princess Luna falls comatose and is revived by the love-sick kiss of one of Celestia's guards. As a reward, she leads him to the ancient hidden barracks of her long forgotten guardian force. Their slowly blossoming romance gives birth to a breed of royal guard not seen in 1,000 years. The Lunar Stallions!

It's been a few weeks since Luna's returned from the moon, and all is not well. She's become more introverted than ever, rarely leaving her room and obsessing over work. Celestia hopes that studying Twilight Sparkle's Friendship Reports will at least help her get out of her shell, though an unusually talkative servant may just help in that regard...and is anypony else getting strange feelings from that statue out in the gardens?

As of May 4th, now featured on Equestria Daily. *Squee*

This story is a sequel to My Little Alicorn

After the events of "My Little Alicorn," everything seemed to be back to normal...except for one pony. Prince Blueblood is now trapped as a colt, his title, possessions and birthright stripped for his crimes. Before Princess Celestia will return him to normal, however, he must prove himself by attending Magic Kindergarten. Even worse, his current situation has attracted the vengeful gaze of two ponies he has offended in the past: the Captain of the Royal Guard and the Moon Princess.

Will Blueblood rise above his past self and emerge a better pony? Or will he sink back into his old depravity, and be stuck a colt for the long term?

Note: This is a sequel to "My Little Alicorn," so you might want to check that out first.

Finding herself with wings and unusually powerful magic, Twilight Sparkle proceeds to have breakdown after breakdown, until with the help of her friends, she confronts Celestia and Luna about it... And learns that she's a far more important little pony than she ever imagined - for all the wrong reasons.

Awesome painting by Drezzer can be found here!

20 megapixel version is here (10MB JPEG, 210dpi strangely, 24"x20")!

Thanks, man!

Princess Luna is back! Purified by the elements, restored to her proper self, and reunited with her sister, the younger alicorn tries to stabilize herself in an Equestria that is not how it once was.

This is a collection of stories.

Back in the Royal Saddle: Luna's first act as returning Princess is to choose the two lucky stallions who will act as her personal guard.

A Week With a Loon: Luna takes over control of Canterlot, so that her dear sister may take a vacation.

Balanced: Luna takes on young Twilight Sparkle as her student.

Of Night Light's and Sound Waves: Luna is "persuaded" to go out at night and explore Canterlot.

After her students release the spirit of Discord on an official field trip, Cheerilee finds herself out of a job. With no opportunities in Ponyville, the schoolmare takes a job offer in the inner city area of Canterlot's old mining town. Can even she overcome the insanities of her colleagues and apathy of her students in time to pass her next annual review? And who is the mysterious backwards-talking filly following Cheerilee around? Luna's School for Disadvantaged Youngsters will never be the same!

Tv Tropes page can be found here.
Cover art based on work by blackgryph0n, used with permissiom.