I dont know what novels and films you studied but ill try to write a starter to your essay!
ok so
Themes developed in (name and other of books and films) all demonstrate the central idea of power of words. For example in (book or film) it states, "
so yea thats a start good luck!!
Johnny Cash was one of few musicians who has ever been inducted into both the rock and country halls of fame.
Theme, I think, the others make sense. Theme is a literary term/device.