"All my life, I've wanted to fly
But I don't have the wings, and I wonder why
I can't break away..."
Most pegasi figure out flying easily enough. Heck, most of them figure out how to do it before they even get their cutie marks.

But not me. I couldn’t do it, no matter how hard I tried. I couldn’t even hover. Not for more than a few seconds, anyway. And not even Rainbow Dash, the greatest flier in Equestria, could seem to help me. We tried everything, and I failed every time. Day after day, I tried – and day after day, I failed, until finally I was ready to just give up. I’d never be able to do it. Nopony would ever be able to help me to fly...

...until one day, somepony did.

What has four legs, wears a bullet-proof vest, can hear you through a solid concrete wall and has a set of highly-trained fangs that can exert up to seven-hundred pounds of pressure per square inch?

One word; Bungee.

Bungee has been a Military Working Dog for as long as he can remember, trained from a pup and turned into a highly effective member of the armed forces. He sniffs out bombs, clears rooms, scouts compounds and assists with flanking manoeuvres to disable dangerous personnel. More than just military equipment; Bungee is a brother in arms. A warrior.

But when a mission goes wrong and Bungee chases a high-value-target through a magical portal; how will the German Shepherd adjust to life among talking ponies?

And how will he manage to complete his mission if he’s considered a pet instead of a soldier?

Rated Teen for violence.

This is a fic based on the Time Loop Files, the format of which was first codified by Innortal on fanfiction.net.
Here's a brief guide.
The basic idea is, one character (the Anchor, usually the main character of a fictional setting) is looping back to the very first moments of their parent series every time either they die or some kind of time limit expires. They of course end up monumentally stir crazy given enough time.
Eventually others start to loop as well.
The reset is not always perfect. Sometimes a loop's history will be different to the "prime" loop, or canonical plot.
"Crossover" or "Fusion" loops also occur, randomly. These can involve the home loopers having a guest, or the anchor for one universe spending time in another, or replacements of one character by another.
Vacation Loops are where the Anchor (or others) decide/s "buck it" and lets off steam by doing whatever comes to mind. There's little or no attempt to maintain the original timeline.

In addition, and particularly more recently, it should be known that this story has a collaborative element to it - people may submit loop ideas or loops, ideally at the Spacebattles thread (a link to the current version of which is on the Trope page), and they may become included.

There's two page image options, thanks to Filraen - the current page image has been edited by the original creator from this work of theirs.. The other one is here:
http://hourglass-vectors.deviantart.com/art/MLP-Loops-466030169

Some accidents are small, and some endow you with the power of a godly ruler. On the opposite end of things, you lose your wings along with your ability to move celestial bodies, and you can't tell anypony. Why, because what would they think if the princess became a librarian? It's going to be "fine". Celestia just needs to switch back with Twilight before either of their true identities are revealed. All Twilight has to do is hold down the castle, fight off scheming villains, run the country, and worst of all... deal with all the noble ponies.

Rated teen for shenanigans and some more serious parts. Takes place at the end of lesson zero. Please tear this apart with comments. I like criticism. Comment if you have issues, don't leave me with a mystery thumbs down.

Rarity comes to Twilight to confess a bizarre secret that will change how Twilight sees her forever. Can Twilight handle it like a seemingly normal, completely well-adjusted and mature pony? Can she even BELIEVE it? (The answers are no, and yes, respectively.)

Raven of the Teen Titans has long been a closet pegasister. She was introduced to Friendship is Magic by Beast Boy and Starfire and - although she is loathe to admit it - she enjoyed it. She especially identified with the character of Twilight Sparkle. What with Twilight's enjoyment of reading, talent in magic, and unexpected but life changing friendships, it felt like Raven's own life mirrored and sugarcoated onto a world of pastel colored ponies. Even Twilight's friends reminded Raven of her own to a certain extent.
When she wakes up one morning in Twilight Sparkle's body with no idea how this happened or how to fix it, she begins to think she identified with her a little too well.
Now trapped in the plot of the series from the beginning, she has to find away to fix this, find out what happened to the real Twilight, and at the same time save all of Equestria. At least she has some friends to help, right?

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Crossover idea inspired by the fact that these two characters share the same voice actor, Tara Strong. Originally, it was just an idea I played with for fun, but I have a serious - and frightening - plot for it. Dark for later chapters.

It is the year 2038, and the Earth is slowly being consumed by a space-borne monstrosity dubbed the Black Tide, which is using nanotechnology to remake the planet into something hideously alien.

Erin Olsen works for Project Harmonics, humanity's last-ditch effort to find a new world before the Tide can wipe them out. But when that world is found, and it turns out to be occupied, Erin will need to find the courage to face the unknown in order to save the inhabitants of both worlds.

(Many thanks to Easteu for the fantastic cover image for this story!)

Now with its own TV Tropes page

There is now a follow-up to this story: Sunflower - Side Projects
Sequel: Project Sunflower: Harmony