George Romero's zombie trilogy has generated an endless parade of remakes and rip-offs, but this clever British spoof comes closer than many to the bitter satire that makes his movies so distinctive. TV writers Simon Pegg and Edgar Wright fully exploit the core gag of most horror comedy, as the title hero (Pegg), a feckless electronics salesman, remains stubbornly oblivious to the gathering danger. But they've twisted this conceit into something much wittier: in a workaday London populated by shuffling, pale-faced drones, Shaun can be excused for not recognizing genuine zombies when he sees them. Pegg and Wright are out of their depth in the second half, when they try to engage the more disturbing elements of Romero's movies, but their disaffected slacker take on the genre is a welcome alternative to the usual bloodbaths. Wright directed; with Kate Ashfield, Nick Frost, Lucy Davis, Bill Nighy, and Penelope Wilton. R, 99 min. a Century 12 and CineArts 6, City North 14, Crown Village 18, Gardens 1-6, North Riverside, 600 N. Michigan, Village.