SCP-173 comes from the SCP Foundation collaborative fiction project and became widely known through the 2012 horror game SCP Containment Breach. In the game the creature cannot move while observed, so a blink lets it close in and kill with a neck snap. That mechanic turned its bone crack into a recognised shorthand online. Clips and edits reuse the sound far beyond the game, signalling an unseen threat, a sudden off screen death, or a statue that has moved when nobody was watching it.