Video of K-On anime characters doing the Miku Miku Dance.
Nekomimi Switch is the title of the song, it’s one of the most popular original creations using the Vocaloid software.
MikuMikuDance (MMD)
MMD is a freeware animation program that lets users animate and create 3D animated movies. It originally features characters from the Vocaloid project, but later on there are ways to switch the models to others.
If you are both artistic and good with computers you can create the models yourself. Otherwise if you just want some fun there are plenty of models available for downloads, which you can further edit or use as it is.
Credits: Daniwell (Nico) and Hino (Nico), via DanPro64 (YouTube)
