Errant tail (in more than one way)
Well, she's definitely a problem child. Her butt is so disobedient it's trying to run away from her body, I think.
I'm not even sure that her tail is where it should be, I think it's just coming out of one buttock.
Maybe I need an "errant tail" tag now too...
(Cover of Problem Children Are Coming From Another Dimension, Aren't They? by Tarō Tatsunoko and Yū Amano, submitted by anonymous)