We all know that Chritopher Nolan likes to have his story as realistic as it gets. He is also very punctilious, so I just thought:
What if he left us hints in The Dark Knight for Joker’s backstory?
Here is my guess:
1.) First of all, Joker is not thinking about himself as a lunatic. (But of course, everyone insane thinks that they are normal.)
2.) This is a keystone of my theory, there is no information about him. How is this possible? He is adult, there has to be something. Someone who remebers him. Guy with scars on his face is quite hard to forget. What if those information are missing because of some reason? What If there was something but someone deleted it? What if Joker was previously included in some secret activity?
3.) Look at those scars. If you are looking closely you may see that they are both different. One is precise, the second one is bit of amateurish. There are two stories Joker told about them, but I think neither of them is right. It’s not so easy. I think he did one of this scars to himself, but the first one not. He was captured and tortured. He went crazy and then he finished his face.
4.) Now, Joker is skilled with dynamite and gasoline. What if his previous activity had something to do with pyrotechnics?
5;6.) As you can see, Joker is skilled in combat fighting too. He not only managed to get policeman but even member of mob guard.
7.) Maybe in this seventh gif he is clearly showing us what was his profession. What if Joker was a soldier? He was captured by an enemy and then tortured. Their mission ended as a complete fiasco so his superiors made him disappeared officially? His problems with authorities may have its origin here.
8.) And this is the only thing we can know for sure. He hates his father. Not just because of his first story he told but here he confirms it. We can’t know if he ever had a wife, but he certainly had father and he loathes him.