Twilight Sparkle and Starlight Glimmer tidy up the library in the Castle of the Two Sisters. What begins as a friendly activity soon turns into magic-based battle of egos and starts to transform the castle into a very dangerous place!
Overused "friends get into an argument with magical consequences" plot. Nothing new added. Also, not Starlight saying it's impossible to make people large more than once to try and sloppily cover a plot hole. Lazy resolution and boring conflict.