All this had started on "Lesson Zero" where Twilight casted a spell on her smarty pants and caused ponies of Ponyville after it. And when Celestia undone Twilight's spell, it almost worked on those ponies. And this was mentioned again when the CMC were sending in stories for Diamond tirara, Applejack saw a picture of Big mac with the smartypants doll. I've wondered if he gave that doll back to Twilight after Applejack fully finds out?