The villain is usually the most interesting part. But it has to be a smart thing. Just dumb cliche villains with a Russian accent and big muscles and a mean face, I don't know. My Russian accent isn't that great, and the muscles aren't that big and the mean face is not enough. You know what I mean? It gets very boring. Tedious stuff.
In any story, the villain is the catalyst. The hero's not a person who will bend the rules or show the cracks in his armor. He's one-dimensional intentionally, but the villain is the person who owns up to what he is and stands by it.
Some of us are born rebellious. Like Jean Genet or Arthur Rimbaud, I roam these mean streets like a villain, a vagabond, an outcast, scavenging for the scraps that may perchance plummet off humanity's dirty plates, though often sometimes taking a cab to a restaurant is more convenient.
I did a play once where a reviewer said, 'Martin Freeman's too nice to play a bad guy.' And I thought: 'Well, bad guys aren't always bad guys, you know?' When I see someone play the obvious villain, I know it's false.
So once I thought of the villain with a sense of humor, I began to think of a name and the name "the Joker" immediately came to mind. There was the association with the Joker in the deck of cards, and I probably yelled literally, 'Eureka!' because I knew I had the name and the image at the same time.