Nani is the Japanese word for what, and as a meme sound it spread through anime clips, reaction videos and short-form edits where a character responds to shocking news. Its popularity grew on TikTok and YouTube, where creators reuse it as a quick shorthand for disbelief without needing any context from the original scene. It sits alongside other anime meme sounds like To be Continued, which creators use for the same dramatic pause before a reveal, and it remains popular because the single word is instantly recognisable across languages and fits almost any surprise moment.