In the wake of opening the School of Friendship and Twilight seeking for more teachers, Fluttershy asks Discord if he would be interested. He said that he will do a test drive by teaching his students a lesson in Philosophy.
After the events of "Discord Teaches Philosophy," the Spirt of Chaos takes up the role of a Substitute. However, after spying on the main teacher, he decides to step in.
Discord's power was something that always frustrated Twilight. All that power, with no effort, no cost. So when Discord offers her a chance to learn his secrets, Twilight quickly agrees. Unfortunatly all things come with a price.
Trying his hand out in being a teacher, Discord starts his first lesson with Celestia. Time for the princess to learn how chaos theory really works. Hopefully things won't get too chaotic, or at least before the test.
Twilight Sparkle is an expert in unicorn magic, but earth pony magic remains a mystery to her. She's determined to uncover the earth tribe's secrets. What she learns will change her life . . . And it just might change Applejack's life as well.