Deltarune is Toby Fox's follow-up to Undertale, with its first chapter released in 2018. Like Undertale, it lets players spare enemies through the Mercy menu instead of defeating them in battle, and that choice became central to how fans talk about both games. Clips of the spare mechanic circulated through gameplay videos, fan edits and short-form posts, where the short menu sound became shorthand for choosing kindness. It remains popular because it instantly signals that theme in under a second.