J: Jonathan Nolan
Christopher Nolan's brother has helped write several films for him. His short story Memento Mori is what Nolan's film Memento is based on. He also helped write the screenplays for The Dark Knight, The Prestige and The Dark Knight Rises showing he has fantastic capabilities as a writer. He works with his brother a lot and apparently said that the reason they work so well together is that he is right-handed and Christopher is left-handed, meaning they can flip each other's ideas and look at them in different lights.
K: Kubrick
Nolan often says, when asked who his main influences are, that Stanley Kubrick was a major influence in his career. Kubrick was infamous for being very persistent in his demands when it came to making a film and would often do dozens of re-takes for scenes because he felt that something was amiss. Kubrick has made some truly fantastic films such as The Shining, 2001: A Space Odyssey, Full Metal Jacket, A Clockwork Orange and Dr. Strangelove. His work is said to be the influence for almost every modern director so it's no surprise Nolan chose him.
L: Ledger's Performance
Heath Ledger's performance as the Joker in The Dark Knight is definitely the best in the entire trilogy. His tragic and untimely death shortly before the film's release meant his performance was watched closely and he really gave that role his best. Nolan quashed rumours that he had wanted other actors like Robin Williams to take the role by saying his first and only choice was Heath. Being a method actor he locked himself away for weeks, trying to see what insomnia felt like and analyse the psychosis of someone like the Joker. In the end, his performance revealed just how hard he tried in preparing that role and it paid off. He won a posthumous Oscar for this which was unusual to see a comic book adaptation win an acting Oscar. After his death though, when we discovered he had died due to an accidental overdose of sleeping pills, people are still trying to figure out if it was indeed his lengthy preparation for the Joker role that took him over the edge.