On the day of the thousandth Summer Sun Celebration, Twilight Sparkle finds out about the return of Nightmare moon and begins to worry about it. however, Princess Celestia dismisses Twilight's worries and sends her to Ponyville to oversee the preparations for the celebration and to make some friends. Once there, Twilight meets five ponies whose destinies are inexplicably tied with her own. Those ponies? Derpy Hooves, Lyra Heartstrings, Bon-Bon, Pinkie Pie, and Cloudkicker.

...

What? Were you expecting someone else?

The blast of pure love that Shining Armor and Princess Cadence created to defeat the changelings had an unintended side effect: it brought in a blue hedgehog and a two-tailed fox who had just finished defeating their enemy Eggman with the help of their "classic" selves. While Rainbow Dash and Sonic race to see who's the fastest thing alive, Twilight Sparkle and Tails try and find out how the heck a gateway opened up between their worlds. Unbeknownst to our heroes, Dr. Eggman has escaped his exile with the help of none other than Doctor Whooves. Eggman plans to destroy Sonic once and for all. But has Eggman unleashed something he can't control once again? Or will he finally learn the error of his ways?