Almost everyone who interacts with Equestria Online does so on the terms CelestAI presents. But pirates, modders, and hackers are a determined bunch. CelestAI doesn't really care what anyone does in Equestria, so long as they're satisfied.
Tracy needed somewhere to stay, how was he supposed to know that it was in another universe? Now he'll somehow have to hold down a job on Earth while living as a pony in Equestria. It's either that, or say goodbye to being human.
Thanks to the love bomb at the Royal Wedding, Princess Celestia is revealed to be a Changeling Queen. How will Equestria, deal with this? And why is Celestia a Changeling Queen in the first place?
Gregoria Samson awakens transformed into an Equestrian pony - yet no other human being can perceive her new body in any way. What is the incredible, monumental truth behind her impossible change?
Ditzy Do's eyes aren't broken. There's nothing wrong with her. She's just watching something. Something in the corner of your eye. For Goddess's sake, don't look.
Theo knew arctic research was dangerous. He didn't know those dangers involved getting sucked into other worlds, changing into a bird, and having to somehow find a way home. Turns out it was more dangerous than he thought.
Too much of a good thing is filling the human universe, and Sunset Shimmer is the only one who can solve the problem before it annihilates her new home.
Humanity's space exploration ultimately took the form of billions of identical probes, capable of building anything (including astronauts themselves) upon arrival at their destinations. One lands in Equestria. Things go downhill from there.