Ponies from across Equestria gathered at Ponyville to witness the first use of a new machine Starswirl the Bearded invented; a machine capable of ripping the fabric of time for a short while and travel through it! The first users? None other than the princesses themselves, much to Counselor Kibliz's dismay. However, something goes terribly wrong when the machine starts up, sending Celestia and Luna wherever, or whenever in Equestria. Next thing everypony knows, weird portals start popping up all over Ponyville. Looks like a job for Twilight Sparkle, Pinkie Pie, Rainbow Dash, Fluttershy, Rarity and Applejack!

But they won't be going alone. As they travel through the past, they'll encounter their foal selves and team up with them. But they'll also encounter younger versions of others as well, including some of their worst foes. With them constantly getting in the way, will the Mane 6 and Baby 6 save the day after all?

Mario and Luigi owned by Nintendo
Cover owned by Rayman2000

AU implied because many things in this story will conflict with the actual canon of MLP. Just sayin'.