You're just an ordinary guy, living an ordinary life. But your life changes one miserable Monday, when you arrive home to find an unexpected visitor in your house: specifically, you discover Twilight Sparkle in your bed.

Things go downhill fast.

And she's just your first visitor.

Tags and contributing authors will be added as needed. A couple new chapters will be added daily until the well runs dry. Continuity is overrated, so don't complain about it. It's a thematic collab, not a big budget Hollywood movie where there are never any continuity errors.
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Winona lies on the grass under an apple tree, reflecting on her life so far. She's lived a long time and she's seen many things in the past, but she likes the present the most, because that's when her friends live the most.

A-A-Additional Character Tags: Tank, Opalescence

Alternate Universe cause quite obviously Winona is not canonically immortal (unless you want her to be).

Princess Celestia asked Twilight to do a census of her new home. Through this process she discovers certain anomalies that she finds strange as a unicorn. There seems to be something missing when it comes to the pegasi, and after much prodding, prying, some spying and begging, she finally gets them to open up. What she discovers is not only shocking (to her, at least), but revealing on pegasi subculture.

Will what she learns change the way she looks at her friends? Will her friendship with them be ruined?

Nah.

Love is a tricky business. Twilight knows this, and the subject has always fascinated her ever since she saw its raw power at her brother's wedding. She is fully prepared to study it in depth... some day. But when Cadance asks her to take part in an experiment that could revolutionize love in Equestria, Twilight realizes that day has come sooner than expected.

If you had a clock that could count down to the moment you meet your soul mate, would you want to know?

Cover art courtesy of Jondor. Go on his page and tell him he's awesome!

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