The notion of ‘social imaginary’ is frequently used in academic publications without any formal definition, which significantly lessens its heuristic value. I take up Castoriadis’ notion of ‘radical imaginary’ and posit its epistemological kinship with a category of Peircean phenomenological analysis of experience, the phaneroscopy, to bring out their combined relevance as a powerful analytical tool of media representations. Peirce defines the category of “Firstness of Thirdness” or ‘Mentality’ as “the color or flavor of mediation”, a little studied notion which I argue can be matched theoretically with Castoriadis' ‘radical imaginary’, namely, the capacity of an individual and of society to introduce what does not exist before into our world of social imaginary significations. The latter is the equivalent of Peirce’s “universe perfused with signs”. My case study is a web series whose topic is a single Latin American nation. The combined theoretical framework is used to analyse the humorous take on national identity of a popular Uruguayan YouTube web series, Tiranos Temblad. Resumen semanal de acontecimientos uruguayos. Each episode is the inventive upshot of its creator’s scavenging, editing and narrating of amateur YouTube videos whose sole subject matter is Uruguay, his own nation. Notwithstanding its single-minded theme, through the use of its eccentric deadpan sense of humor and amusing collage of disparate videos, the series is an emblematic example of how the notions of radical imaginary and Mentality can account for the creation of a groundbreaking post-nationalistic media artifact regardless of its apparent praise of one nation.