A theme that is often presented in various zombie mediums, such as Romero's Dead films and more recently in The Walking Dead TV series, is that humans are often a bigger threat to humanity than the flesh-eating monsters. For Shaun of the Dead, the monster in their midst is David (Dylan Moran), who obviously has a thing for Shaun's girlfriend, Liz (Kate Ashfield), even though he's dating her friend Dianne (Lucy Davis).
While David is not quite as threatening a villain as the nefarious Negan (Jeffrey Dean Morgan) of The Walking Dead, he does demonstrate the selfishness and desperate lengths that some humans are capable of. David tries to undermine Shaun at every turn, resentful that his rival has taken on the leadership role. He even points the Winchester rifle at Shaun's mother after the discovery that she has been infected, leading to a tense standoff between himself and Shaun wherein David appears all too eager to pull the trigger ... on Shaun, that is.
