Neco-Arc is a joke cat counterpart of Arcueid Brunestud, created for Type-Moon's Tsukihime universe and best known to many fans through the Melty Blood fighting games. Her exaggerated, nonsensical behaviour made her a favourite for memes, fan art and short edit clips, where a single strange vocalisation can stand in for her whole personality. The niiin sound circulates in that meme context, shared as a reaction noise for chaotic, cute or deliberately confusing moments. Its brevity keeps it easy to reuse, and its recognisable link to Neco-Arc gives even a one-second edit an instant in-joke for fans.