Formally published content represents a tiny fraction of all created content. There are far more outsider creators (including fan authors) than there are insiders. A sufficiently well realized fictional world is one to which fans will want to return on self-guided adventures: fans explore their favorite worlds by creating fan works, and economics inexorably dictates that fans are more numerous than insider creators. The success of, say, Harry Potter depends on an audience of billions. Creating and sharing fan works is an important part of the process of enjoying a work of fiction; the ratio of Harry Potter fan works to canonical Harry Potter texts is probably over a hundred thousand to one. This chapter examines the unclear copyright status of fan works, beginning with an overview of fan works, then examines those works under U.S. copyright law, and finally seeks possible accommodation that can serve the interests of all.