In my review of Shaun of the Dead, I praised its attention to detail and the thought that went into the continuity of the film.
If you need any more evidence to believe this to be true, just take a look at this collection of images, before and afters, of extras in the film. While some reappearances may have seemed obvious, others are discretely slipped into the undead menagerie. It’s a nice nod to the world it's set in. Not many zombie films have this touch yet it’s common sense that those in the background before the end of the world would become those hunting you down when it all ended.
