This isn't the first time the author has done this. An earlier show of his, Soul Eater, has a character that is a cat with the ability to turn into a woman. She doesn't have any clothes on when in her human form, and she loves to prank the human characters by transforming at the worst times. Fortunately, she is only the protagonists roommate, so you can go episodes at a time without seeing her, since the gang leaves her at home when they go out on missions.

I wonder if that was spite fanservice too?