Supernatural is a TV series which ran from 2005 to 2020 created by Erik Kripke that follows the journey of two brothers who hunt monsters, ghosts and creatures from different urban legends, folklore and mythological tales. This paper intends to explore the Supernatural universe as a transmedia product. First, it analyses the expansion of the show, as it not only consists of the fifteen-season show but also in several different media in which the story has been developed. Secondly, it explores the use of fanfiction and its implementation in the narrative of the show, making use of the prosumer’s creations so as to further broaden the plot of the show. After this, it develops an analysis of the use of metafiction which has become a central feature throughout the fifteen seasons the show has run. Additionally, this paper goes deeper into the concept of Expansion by analysing the idea of spin-offs, taking into account the one already in development by the company in charge of the show and the one which was not picked up by the network. Lastly, this paper dwells on the use of music as a possibility for the expansion of the story. Finally, in every section of this paper, it is shown how Supernatural integrates the result of such expansion into the narrative of the main story itself. All of the aspects mentioned before are the ones that contribute to the transformation of Supernatural into a Transmedia product by expanding its universe through different media and inside the show itself.