Undertale is Toby Fox's indie RPG released in 2015, and many of its sounds and character noises have been clipped and reused online ever since. Short game audio like this spreads easily in meme edits because it is instantly recognizable to players and easy to drop into fast videos. It still shows up in gaming posts, reaction memes and retro-style edits where creators want a cute, odd little sound instead of a heavier hit like a vine boom sound.