League of Extraordinary Gentlemen crossover set in 1936, featuring among others The Shadow, Mary Poppins, Lord Peter Wimsey and Dorothy Gale (and her little dog too!).
Superb, marvelous stuff, packed with easter eggs and flows along beautifully. One of the best stories I've read in a long, long time.
WARNING: Although complete up to a point, the story is set up to continue in another fic which does not seem to be available yet.