This paper analyses the linguistic construction of the televisual character Sheldon--the "main nerd" in the sitcom "The Big Bang Theory" (CBS, 2007-), approaching this construction of character through both computerised and "manual" linguistic analysis. More specifically, a computer analysis of dialogue (using concordances and keyword analysis) in series 1 of "The Big Bang Theory" provides insights into how Sheldon is constructed through both explicit and implicit cues in his own and others' dialogue, drawing on shared stereotypes of "nerdiness". This corpus linguistic analysis is complemented through manual, "scene-based analysis" of implicit cues in dialogue between Sheldon and Penny, drawing on (im)politeness theory. Previous analyses of film and TV dialogue have shown how linguistic deviance, e.g. in terms of politeness, can construct characters as somehow "anti-social", "abnormal", "rude" or "not quite human". The analysis of Sheldon's repertoire provides insights into how and when linguistic deviance constructs nerdiness in contrast to other social identities. This allows us to consider which factors lead to viewers' perception of characters as threateningly abnormal or funnily abnormal or somehow non-human or indeed as other social identities. The analyses also show how dialogue projects a particular social identity drawing on stereotypes and shared knowledge with the audience. (Contains 7 figures, 3 tables, and 8 notes.)