Drawing books is fun! The pic would have taken a lot less time to finish if every freaking book hadn't been drawn, but meh, Twilight justifies such things.
A magic mirror that leads to a world where Twi and Sunset met as Royal Students, becoming friends as they bonded over a shared love of Magic and Princesses... how cute would that be?
Darn it, Celestia. Why you no buddy up your students? Though I'm still not sure when exactly Miss Shimmer left, so maybe Twi wasn't even discovered by then. Either way, certainly wish they'd had the chance to meet on friendlier terms!
In any case, this world has a Celestia who is actively friendshipping Sunlight~ -w-