Zombies, mostly referred to in-universe as Walkers (but also referred to as geeks, roamers, lurkers, biters, sickos, infected, bobbers, lamebrains, eaters, and guardians) are an antagonistic force that serve as the primary catalyst for the events within The Walking Dead universe. They serve as universal antagonists. Zombies or Walkers within The Walking Dead universe are Robert Kirkman's version of George Romero's Night of the Living Dead zombies.