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

After discovering that Cadence is not who she appears to be, Twilight is sent to another world entirely by the disguised Changeling Queen to avoid her plan being disrupted.
When Twilight lands, she discovers that not only have Spike, Owlowiscious and Peewee followed her, but that they've arrived in a world where the main sentient species is human.
There's still a place where they teach magic, though.
Crossover with Harry Potter. Twilight will be effectively taking the role of Hermione.

I've marked this story as cancelled to reflect the unlikelihood of it continuing. If I do come back to it I'll revert that.

Based on the image, by Equestria-prevails on Deviantart. Two guards, one Day and one Night, having a drink on their night off.
This more or less came about when I wondered at the backstory of the image, saw several other people doing the same, then decided to make it happen.

What is the nature of an oath? What is camaraderie?
And what should a guard do, when his background has secrets buried within?

The story of the newly promoted Admiral Twilight Sparkle, and her first command. A fusion fic with various science fiction series by David Weber, principally but not only the Honor Harrington books.
Cover image from Kampzvono on Deviantart, used with permission.

There's more than one way to lead, and more than one way to be an Element of Magic. An AU looking at the effects of a slightly different early life for two unicorns.

So yes. This resulted from wondering what Trixie would be like as an Element of Magic. Given the choice, I decided to make her and Twilight childhood friends because of the potential for their entire life to be a gigantic Bokke and Tsukkomi routine (a comedian/straight man routine).

I also think that Trixie would do well as a combat mage. After all, she's genuinely powerful (if not so powerful as Twilight) and more importantly she's very good at misleading and bedazzling others. In fact, this entire thing began with my writing the fight scene with Nightmare Moon.

Finally, the Discording she had is based in part off what happened to her in the Pony POV series.

Hope this at least gave you the odd laugh.