You play as Anthony Williams, a homeless person in Los Angeles who doesn't give a shit. One day, as he is again blocking the highway with his shopping cart, a plane full of biowaste crashes into the bridge nearby and one Bad Day in L.A. begins. Soon people begin to mutate into zombies because of the dangerous waste, meteorites come down from the sky, a tsunami makes its way to L.A. and many other bad things happen. The game is a humorous take on the USA's post-9/11 culture of fear.
Your only goal is to survive. You can do that by either shooting your way through everything and anyone, or helping the people around you. You need to protect them from terrorists, street gangs or zombies with the help of eight weapons from a tire iron to a rocket launcher. But you can also heal the zombies with your fire extinguisher or use it to help burning people. For every action you do, you either get a smiley or a frowney, and depending on how many of these you have collected, the NPCs will have different behaviours. If you behave like a psycho and collect frowneys, everyone will hunt you down and will not help you find your way through the mess.