Unless you've been living under some kind of cavern, from which even the slightest of foreign pop-cultural phenoms cannot penetrate (in which case, congrats on being able to find Topless Robot in your Luddite rock dome!), you've probably seen a few things featuring the precociously cute Japanese idol Hatsune Miku.
Who is Hatsune Miku? What is she? What does she do? There's two ways to answer that.