User blog comment:FanOfStuff/Art blog 1/@comment-1153194-20111130210557/@comment-1874924-20111201024803

The TV Tropes site calls the exaggerated hips "Hartman Hips" after a certain artist who favored that style (if memory serves). The purpose of the wide hips is to make a girl look more mature without having to give her big boobs, although most of the canon TD girls have those as well.