Oh and Nolan never even hide the fact that he did change the characters and that he adjusted them for his world
Christopher Nolan: To be honest, myself and David Goyer, we really just kind of dove in and tried to do our version of the character simply based on our memories of the comics without going back to research.
Its a very interesting thing to sit around and think with Batman Begins as a prism for how you view Batman, how does that effect the way you see the Joker. Who would that guy be in our universe? (CBR interview, 2008)
Ultimately we just got caught up in that process of imagining how you would see a character like The Joker through the prism of what we did in the first film.(...) let me put it this way, our Joker - Heath's interpretation of The Joker has always been the absolute extreme of anarchy and chaos, effectively - he's pure evil through pure anarchy. (Empire Magazine #229)
thinking about what this icon is when viewed through the prism of Batman Begins. When viewed in the world we created, in the tone we created. And what we arrived at is somebody who is quite a serious guy, really, considering his name's the Joker and that turned out to be quite similar to his original conception. (IGN)
In comic books Joker was a clown, an entertainer who was like a ringmaster, always energetic and having fun and clownish fun when comitting crime. He was an entertainer, and thats why he was CLOWN prince of crime. Dancing, singing, using all the fun gadgets and circuses and amusement parks as his hideouts. He acted like a real clown, changing clothes very often, playing dress up. And he was a deformed freak. And from his inception throughout over 4 decades he was a thief stilling $ and diamonds. Nolan's Joker is an idealist and anarchist who, unlike his comic book counterpart, didnt care for his own life at all, didnt care for reputation, that hes gonna look bad in front of other Batman villains (like Hammil's Joker did too), didnt fear anyone and dint have an oversized ego. This Joker also either didnt feel or enjoyed pain, he was a masochist
Christopher Nolan: His chief motivation is that of an anarchist. I talked to Heath a lot about it even as we were finishing the script, and we both agreed that the most threatening force society faces is pure anarchy (CBR Interview, 2008)
I talked with him about the anarchic elements that I saw as being the more realistic Joker, the guy who would actually frighten an audience, and he'd already come up with a lot of that on his own. We talked a lot about Alex in A Clockwork Orange, people like that. He'd come up with the same things independently.(Empire Mag #229) CLockwork orange - not comic book Joker. They read the early comics only after they already wrote the script and developed the character
Christopher Nolan: We didn't look at those first stories until after we'd come up with our story and Jonah started working on the job. It's a weird thing. He called me up halfway through his job and said, "By the way, have you looked at his first and second appearance recently?"(IGN)
The point of all this, changing characters doesnt mean squat to me. Never did. The quality counts, whats interesting counts. And this take on Joker was certainly interesting, as was Penguin in BR.
BR and Nolan's movies changed characters radically to fit their vision, so what? They rocked, they were fleshed out, and they were surely interesting and most importantly - they served the story
