Subtext undertone is any content of a creative work which is not announced explicitly by the characters or author, but is implicit or becomes something understood by the observer of the work as the production unfolds. Subtext can also refer to the thoughts and motives of the characters which are only covered in an aside. Subtext can also be used to imply controversial subjects without specifically alienating people from the fiction, often through use of metaphor. Especially in light of their inherently ambiguous and self-referential character, many authors have explicitly used subtexts (or subtexts about subtexts) in humor.