Regardless of how you might feel about all of the directors who have handled the Batman franchises - and those who will in the future - one unavoidable thing is that each of them has created something that pays open homage to the source. Such is the nature of the beast - the films are interpretations, and even the most removed - the films of Nolan - had to express similarities to keep the Batman fans engaged. Yes, some - Schumacher - lacked the restraint and self-awareness to really make anything good, but he showed exactly the same joy for Batman, and indeed for film-making as a whole as Burton and Nolan did. He just got over-excited and nobody told him to calm down. As a result of that filmic awareness and passion, each of the Batman films, from 1989 onwards, were positively rammed with in-jokes, references and Easter Eggs, and as Batman film fans we owe it to the film-makers to acknowledge and celebrate the very best of them.
21. The Joker's Mask
The Joker's heist masks that he and his cohorts use in the opening of The Dark Knight could well just have been a reference to exceptional classic heist movie The Killing, and nobody would have batted an eyelid. Nolan loves film after all. But it goes beyond that, as the mask was subsequently discovered to be a reference to the 1960s TV show, and the 1966 episode "The Joker is Wild" in which the Joker (Cesar Romero) dresses as Pagliacci. The similarities are too compelling for it to have been a coincidence, and it seems Nolan paid homage even to the least loved version of the Caped Crusader.