Everypony knows that Pinkie Pie is one of the best bakers in Ponyville. However, one pony is better at making muffins then even the party pony herself and that is Ponyville's clumsy mailpony: Derpy. Her secret? Using deductive reasoning and logic to figure out what type of muffins would be best for certain ponies based on their mood, behavior, looks, mail, and more.
Upon learning this, Pinkie Pie sees a way to give more joy to those she cares about with her treats and asks Derpy to take her on as a student.
*Commissioned and Edited by Grand_Moff_Pony*