Hatsune Miku is a character that is for some reason on the cover of a speech synthesizer, like Microsoft Sam or MacInTalk, specially suited for making J-Pop songs. The cover of which can be seen on the Wikipedia page or
here. The character has been popular among weeaboos (or anicigarettes, or wapanese, or whatever you like to be called) for quite some time. The forum seems to just recently be catching on to it, especially with so many members getting very seriously into anime all of a sudden.
I'm not particularly happy about it myself, having seen enough of that character over the past two years or so, but whatever.