Mixed Genres and the Platypus

Authors are having a lot of fun playing among the traditional genres these days.  In an era when Pride and Prejudice and Zombies, Abraham Lincoln, Vampire Hunter, and the movies "Ninjas vs. Vampires" and "Cowboys and Aliens" are popular, we might well question whether the term 'genre' has any meaning any more.

What is (or was) a genre?  It's "a category of artistic works based on form, style, or subject matter, into which artistic works of all kinds can be divided."  In its entry on genre...