I think that my favourite sub-genre of fantasy comedy would be the rewritten fairy tale. Probably the best example of this is Terry Pratchett's Witches Abroad which has among other things a rewriting of Cinderella. This can also be seen in Shrek with all the fairy tale creatures as minor characters. Some other books which do this include some of Tom Holt's work like Snow White and the Seven Samurai, which has: Snow White, Little Red Riding Hood, the Three Little Pigs, The Big Bad Wolf, and others. Another good example is the Hollow Chocolate Bunnies of the Apocalypse, by Robert Rankin where a teddie bear and a boy detective named Jack attempt to solve mysterious fairy tale murders of Jack Spratt and Humpty Dumpty.

An example that I have not tried yet is Nursery Crimes by Jasper Ford. If anyone knows the vibe I am going for I would love to hear it.

A more serious example by a few of the writers of Lost is Once Upon a Time a 7 season tv show about fairy tale characters in the enchanted forest and in our modern realm.