Undyne is a major character in Undertale, the 2015 role-playing game by Toby Fox, and her Undying form appears during the game's genocide route as a far stronger version of the fish-like warrior. Clips of that encounter have circulated for years in gameplay videos, edits and soundboards, where short dramatic cues are easy to reuse out of context. This appearance sound is popular because it works even without the full battle, giving creators a quick way to signal that a familiar character has returned stronger, angrier and ready to fight.