The Undertale death sound comes from Undertale, the indie RPG created by Toby Fox and released in 2015. Because the game became hugely popular online, its failure and game over audio quickly spread into YouTube edits, livestream highlights and short meme videos. Creators still use it because the cue is brief, recognizable and easy to understand even for viewers who have never played. It fills a similar role to the Roblox oof in clips built around mistakes, defeat or sudden embarrassment.