Stalkers are the gaunt, surgically altered prisoners first seen in Half-Life 2, released by Valve in 2004. In the game they shuffle through Combine facilities and let out strained, distorted screams that underline how dehumanised they have become. Clips of those vocalisations were later ripped and shared on forums and video edits, where the shortest scream became a reusable scream meme for horror jokes. Its gaming origin is instantly recognisable to Half-Life fans, which helps explain why the sound still appears in mods, remixes and meme compilations long after release.