Hatsune Miku is a virtual idol that was originally created for Yamaha Vocaloid software. Now, Hatsune Miku pops up in her own Sega music games. Meaning? People wearing ridiculous Hatsune Miku costumes at Sega events!
The costumes themselves are rather freakish -- even freakier when you consider that there is a person in there waving hands and looking happy.
I did not do the delightful Microsoft Paint drawing. Somebody on the Japanese internet did that, so tip your hat to him or her.