If you haven't seen this movie, watch it. It mixes great world building techniques with flash backs and illustrates fantastic character development. And the rules the main character develops to survive in a land of zombies are hilarious with a level of truth.
Robert Mckee, author of the popular book, Story, distills every story to be a quest. Romance stories are quests for lust or love, fantasies are quests to save the helpless, thrillers are quests to solve a mystery of some sort, etc.
The main character, Columbus, played by Jesse Eisenberg is a college student who's on a quest to find out if his parents are still alive. Alive as in not zombies. Honorable endeavor.
Columbus and Tallahassee run into a pair of sisters played by Emma Stone and Abigail Breslin whose sole purpose is to survive.
But Woody Harrelson plays Tallahassee. What's his quest? Is it to save a damsel in distress? No. Is it to find the one rare cure for zombieism? Not even close. He loves killing them. How about to rescue other humans from being eaten? Ha! Nope. His quest is an honorable one. Twinkies.
This brings us to the whole message of the movie. Enjoy the little things in life. Because in the world of zombies, (i.e. a symbol of our world: people who work, do as they're told, consume, watch mindless TV, and sleep only to wake up to do it again) you have no choice but to enjoy what you love. And it's usually the little things that matter the most.