This sound comes from Undertale, the 2015 indie RPG created by Toby Fox, where each main character has a distinct dialogue noise. Sans became one of the game's most quoted and memed characters, so his text sound spread far beyond gameplay clips into meme edits, TikToks and joke dubs. People often use it as shorthand for a lazy, ironic or unfazed response. Its popularity has lasted because even a split second of the sound is enough for many players to recognise Sans immediately.