This year's theme, "Potluck," invites everyone to bring something to the table-costumes, creativity or just good energy-because, as the organizers put it, "when we do it together and care for one another, there is enough for everyone." Expect a dazzling, chaotic mix of 50,000-plus zombies, witches, robots, Jedis and other creatures of the night marching up Sixth Avenue from King Street to 15th Street between 7 and 11pm.