Joel and Ethan Coen make two types of films. Both types are comedies.
The first type sometimes gets mistaken for a drama. They’re the dark comedies that usually operate within a specific genre. Some of these are easily spotted – even Wikipedia calls Fargo a comedy – but it’s easy to get distracted by how serious they look on the surface. The Man Who Wasn’t There is a black-and-white period noir, which somehow overrides that the whole film is set in motion by someone coming up with this totally crazy idea he’s calling “dry cleaning”. The closest to a true drama that the Coens have directed is probably No Country for Old Men, but it has a huge amount of funny hair for a very serious, tense movie.