The most popular version of The Joker in recent years, without a doubt, is Heath Ledger's portrayal in Christopher Nolan's The Dark Knight. The actor produced not just one of the best versions of the character ever seen, but also one of the most electrifying and terrifying bad guys in movie history. He was really, really bloody scary. Apparently the actor spent months beforehand working on his persona, filling notebooks with long treaties he wrote in-character. It definitely shows in the finished film, with The Joker appearing to be a fully-fleshed out human being for the first time ever. Well, in a manner of speaking. Nolan's Joker is also totally different from any seen before, the closest you could get to him existing in the real world. He's essentially a terrorist, albeit a nihilistic one who creates chaos for no real reason apart from his own entertainment.