User blog comment:Miskos3/Fairy Tail Chapter 320: Roaring Thunder, Review/@comment-121.54.8.130-20130226062537/@comment-121.54.8.130-20130228080051

i believe that the Zentopia affair in the anime was Mashima's idea that he passed on to the animators so that he can get ahead many chapters. By that time, the anime was catching up to the manga.