A comparative approach leads this paper’s analysis of two short stories by George Sand and Jean Lorrain, Mouny-Robin and « Lanterne magique », stories separated by almost sixty years (1841 and 1900), but similar through their structure (embedded narration), their musical themes (two opera performances, Carl Maria von Weber’s Freischütz and Hector Berlioz’La Damnation de Faust), and a common issue (the future of the fantastic genre or in general of fantasy within a positivistic environment). This study brings to light the art and manner of fantastiquer, or fantasize and create a work of fantasy – for each of the authors : for Lorrain a fin-de-siècle type of fantasizing in a decadent spirit which tends to plaster over reality with images whose goal is to make it uncanny, and, with Sand, more picturesque and « folkloric » types of fantasy.