For the Robert A. Heinlein short story collection, see Expanded Universe (Heinlein).
The term expanded universe (sometimes called an extended universe) is generally used to denote the 'extension' of a media franchise (i.e. a television show, series of featured films, etc.) with other media (generally comics and original novels). This typically involves new adventures for existing characters already developed within the franchise; however in some case entirely new characters and complex mythology are developed. This is not the same as an adaptation, which is a retelling of the same story, usually on a different medium. Nearly every media franchise with a committed fan base has some form of expanded universe. A very popular example of this is fan fictions. Fan fictions are stories created by a fan base that portrays existing characters in new and different ways.