Imaginary worlds are one of the hallmarks of modern culture. They are present in many of the most successful fictions, be it in novels (e.g., Harry Potter), films (e.g., Star Wars), video games (e.g., The Legend of Zelda), graphic novels (e.g., One piece) and TV series (e.g., Game of Thrones). This phenomenon is global (e.g., the emergence of xuanhuan and xanxia genres in China), and massive (e.g., the worldwide success of Lord of the Ring). Why so much attention devoted to nonexistent worlds? We propose that imaginary worlds in fictions co-opt exploratory preferences. Imaginary worlds are fictional superstimuli that tap into the human’s evolved interest for unfamiliar and potentially rewarding environments. This hypothesis can explain the cultural success of specific artefacts, such as maps in fictions, and the cultural distribution of such fictions across time, space, and individuals. Notably, this hypothesis makes predictions that rely on previous research in psychological and behavioral sciences: 1) fictions with imaginary worlds should be more appealing for individuals higher in Openness to experience (because this Big Five personality trait is associated with exploratory preferences), 2) such fictions should be more attractive for younger people (because young people reap more reward from exploratory behaviors, thanks to parental investments, and are thus adaptively more motivated to explore) and 3) such fictions should be more successful in more economically developed societies (because affluent and safe ecologies lower the costs of exploration, and phenotypic plasticity thus promotes exploratory preferences). We successively tested these predictions with two large open-collaborative datasets, namely IMDb (N=85,855 films) and Wikidata (N=96,711 literary works), and with the Movie Personality Dataset, which aggregates averaged personality traits and demographic data from the Facebook myPersonality Database (N=3.5 million). We provide evidence that the appeal for imaginary worlds relies on our exploratory psychology.