Kizuna AI is one of the best known early virtual YouTubers, debuting on YouTube in 2016. Short reaction snippets from her videos spread widely in anime and meme communities because her expressive delivery is easy to clip and reuse. This “WTF” sound became useful as a fast reaction insert for edits that need surprise, confusion, or disbelief in less than a second. Its staying power comes from that recognisable VTuber voice and the way it fits modern short-form reaction humor.