Part of the /Alternative series.

Twilight Sparkle was a talented university student under the guidance of Princess Celestia herself.
Rainbow Dash was a juvenile thrill-seeker barely scraping by from one near-death experience to the next.
Rarity and Pinkie Pie started off as two strangers in a train station.
Applejack and Fluttershy were just trying to survive in the big city.

Some way, some how, they were all invited to the same event, and before the day was over, they became the only things keeping their homeland from eternal darkness and ruin.