Hmmm... I am not sure if this counts, but the main heroine from "
Concrete Revolutio", one of this season's anime series, suddenly went out of control in the end of this week's episode and temporarily turned into a darker version of herself that is referred as the future queen of devil realm. From the transformation, it seems her personality changes and her hips slightly expands. It happens in the
11th episode around
20:12 mark.
You can watch the episode here:
http://gogoanime.tv/concrete-revolut...sou-episode-11