Online television audiences create a variety of digital content on the internet. Fans of television production design produce and share such content to express themselves and engage with the objects of their interest. These digital expressions, which exist in the form of graphics, text, videos and often a mix of some of these modes, seem to enable participatory conversations by the audience communities that continue over a period of time. One example of such multimodal digital content is the graphic format called the animated GIF (graphics interchange format). This article focuses on content creation by online audiences who use the blogging service Tumblr and analyses the animated GIF – a web image format that is able to display a succession of frames – from a multimodal and social semiotic viewpoint. The author analyzes animated GIFs as digital content, and frames digital content creation as design, both in the sense that multimodal meaning making is an act of design and in the sense that web-based graphics are designed graphics that are created through a design process. She specifically focuses on the transmedia television production entitled Lost and analyzes the design of animated GIFs related to Lost in participatory online platforms. Therefore, this article aims to understand the role of GIFs in online communication as a transmedia literacy practice through a case study of the creation of GIFs within the Lost fan community on Tumblr.