The line comes from the opening cemetery scene of George A. Romero's 1968 film Night of the Living Dead, spoken by Johnny to his sister Barbara as he pretends a nearby stranger is a ghoul. Moments later, that stranger attacks, launching the zombie genre as modern audiences know it. The quote survived because it is short, quotable and tied to a landmark horror film, and it has since been reused in Halloween compilations, horror retrospectives, reaction videos and memes that warn someone trouble is approaching.