Fanfiction is the creative appropriation and transformation of existing popular media texts by fans who take stories, worlds and/or characters as starting points and create their own stories based on them. As a cultural field of practice, fanfiction questions prevalent concepts of individual authorship and proprietary of cultural goods. At the same time, fanfiction itself is challenged. Through processes of mediatization, fanfiction grew and became increasingly visible. Third parties, ranging from the media industry (e.g., film studios) and copyright holders to journalism and academia, are interested in fanfiction and are following its development. We regard fanfiction communities and fan acting as fields for experimentation and as discursive arenas which can help understand what appropriating, writing and publishing in a digital culture and the future of writing might look like. In this paper, we outline important debates on the legitimacy and nature of fanfiction and present preliminary results of current research within Germany