I'd like to say the same for Shaun of the Dead but I felt that went a bit too over-the-top and really should've known better.
You know what? I'm going to take this and run with it because I think it's one of the movie's crowning achievements. The whole movie is fall down funny, one of the best British comedies I've ever seen and then out of nowhere they pull the rug out from under you!
When Shaun's mother reveals the bite, the entire tone of the movie shifts gears and it slowly builds to this horror movie climax. The next fifteen/twenty minutes make Shaun of the Dead as relevant as any other zombie movie because of this part. I think it legitimizes the movie and qualifies it as much a zombie movie as Dawn of the Dead.
They do it again in Hot Fuzz going into the third act.
