After the mids, the subgenre was mostly relegated to the underground. The narrative of a zombie apocalypse carries strong connections to the turbulent social landscape of the United States in the s, when Night of the Living Dead provided an indirect commentary on the dangers of conformity, a theme also explored in the novel The Body Snatchers and associated film Invasion of the Body Snatchers Zombie walk and Zombie Squad The zombie also appears as a metaphor in protest songs, symbolizing mindless adherence to authority, particularly in law enforcement and the armed forces. This list includes a company in California, Harcos Labs, that sells bagged Zombie Blood and Zombie Jerky in specimen style pouches;  In music Michael Jackson 's music video Thriller , in which he dances with a troop of zombies, has been preserved as a cultural treasure by the Library of Congress' National Film Registry. Zombies take full control, while small groups of the living must fight for their survival. Martin's Press stated "In the world of traditional horror, nothing is more popular right now than zombies Such stories are often squarely focused on the way their characters react to such an extreme catastrophe, and how their personalities are changed by the stress, often acting on more primal motivations fear, self-preservation than they would display in normal life. The researchers explain that their methods of modelling may be applicable to the spread of political views or diseases with dormant infection. Zombies are slate wipers. Romero 's film Night of the Living Dead. Victims of zombies may become zombies themselves. In second place was Living Corpse and in third, Biomega , which he called "the greatest science-fiction virus zombie manga ever".