Mikudayo is a nickname given to the human-size costume (kigurumi) of Nendoroid Hatsune Miku. The costume was shown for the first time at the Tokyo Game Show 2011 to promote the Nintendo 3DS game Hatsune Miku and Future Stars: Project Mirai. However, folks felt that there was something odd about the costume - perhaps even scary ^^;
Mikudayo's scary form has made her popular among the Japanese otaku community which prompted a load of interesting photoshopping. Good Smile Company seized the business opportunity and brought out not only a Nendoroid of her but now we are blessed with a 1/8 scale vinyl figure too^^;
Head along to Good Smile Company for more info about Mikudayo.