This sound comes from Plants vs. Zombies, the tower defense game released by PopCap in 2009. The warning line became memorable because players hear it right before zombie waves begin, tying it to rising tension and fast decisions. Online, the phrase spread beyond the game into short edits, memes and gaming compilations as a simple way to announce incoming trouble. It is still used because the line is instantly recognizable to many players and works even for viewers who never played the game.