SCP-173 comes from the SCP Foundation fiction project, where the creature is famous for moving when unobserved and snapping victims' necks. Sounds like this became common in fan videos, gameplay clips, and horror edits built around that idea. The clip stays popular because it is instantly readable even without dialogue: one crack tells the audience exactly what happened. It is often used in SCP game content, analog-style horror posts, and short meme edits that rely on a quick, brutal payoff.