This sound is associated with Hatsune Miku and is widely shared as a tiny anime reaction clip, with published source notes pointing to Jashin-chan Dropkick. Short “nani?” clips spread easily on soundboards, meme edits and reaction videos because the meaning is instantly clear even to casual viewers. It stays popular thanks to its compact timing and familiar anime tone, similar to how creators use other surprise reactions like eh?eh?ehhhh? when they want a fast, exaggerated response without needing a long spoken line.