Nightmare Moon is defeated, Ponyville is celebrating the return of the sun and Princess Luna finds herself a thousand years from the world she knew, where even apples are strange.
Princess Twilight Sparkle writes pony history by opening a portal to another world and making first contact with extra-Equestrian intelligence. Only snag: the portal opens at a pony ranch on Earth.
At Discord's urging, Princess Twilight hops on through the mirror portal to Canterlot High, which had been closed for two millenia. Instead of a school, she finds herself in a cargo bay of a starship. Discord also has popcorn at the ready.
In the face of anon-a-miss, Sunsets runs away to Equestria to get a break and finds a welcome relief in her old life as a pony. Cultures clash as her CHS friends, determined to win her back, discover just how little they know about Sunset.
Something has happened and Twilight finds herself in a strange and dark new world. The Bipeds here have strange magic, advanced technology, and a lot of problems. She needs a few friends, and they just might need her. WORM crossover.