Nani is the Japanese word for what, and its sharp, questioning delivery has long been a staple of anime reactions to shocking news. Online, the line became a widely shared meme sound, used whenever a character or creator needs an instant double-take. Bass-boosted versions followed the wider bass-boost meme trend, exaggerating the impact for short edits and reaction videos. It remains popular because the meaning is instantly clear even to viewers who do not speak Japanese, and the boosted low end makes the surprise impossible to miss.