Princess Twilight Sparkle receives a letter from Princess Celestia. The letter is simple: Celestia has a new student. Feeling a little put-out by this, Twilight goes to talk with her and clear the air.
Equestria has resources not found in any other dimension, so of course an alcoholic, mean-spirited scientist would get in on that and drag his grandson along for the ride.
Zevan was a loyal changeling and did his queen's bidding, although he questioned why she had broken the peace. After being badly injured though, he had to reconsider his future, and a unicorn mare with a broken horn was a surprising part of it.
Dandelion is Cogs' firstborn daughter, and a joy to him and his wife. As a changeling though, Cogs had no experience with raising pony foals, so when a crisis arises, he often has to wing it. Sometimes the solutions are more creative than others
Twilight has agreed to host Princess Celestia for a three month vacation. When she meets her disguised form, she sees her teacher in a whole new light.