Shaun Of The Dead has defined a new film sub-genre: rom-zom-com (romantic zombie comedy). It's directed by Edgar Wright, who previously worked on UK TV sitcoms such as Spaced. The lead actor (and co-writer) is Simon Pegg, who was also a Spaced cast-member.
Pegg plays Shaun, whose dull life is interrupted by a plague of slow-moving zombies (a la Dawn Of The Dead). However, because he's so used to seeing drunks and beggars on the streets, he doesn't realise that they are actually zombies. Several scenes show people going about their daily lives in a state of somnambulistic catatonia - are the undead zombies really any different from these mindless commuters?