After a long, quiet day of reading, Twilight picks up another book. Well, what else was she gonna do, Sherlock? Sleep? Of course not. There's far too much to learn. This book she picked up was different. Blasphemous. It suggested that Celestia and Luna may not have created everything around her. But Twilight was open-minded, she always has been, so she carried on reading. It explained about something called "Multiverse Theory".
After that... Well, that's when the weird stuff started happening.