That above picture reminds me of something I was thinking about yesterday. The drill was pretty phallic looking, and the fact that it was "penetrating" the wall, that was just icing on the cake. So later, Azula (and Mai and Ty Lee) got inside of Ba Sing Se..
So.. Azula raped Ba Sing Se, but then she also ended up being the "invader". That girl can be anywhere; she's the "father" and the "fetus" at the same time.
***SPOILER***
This is what a combination of boredom, stress, fatigue, and AWS can do to you.