This was a kind of parasite creature for an online campaign that I did once. The players never got far enough to name them, so I'll call them 'Boogity-Boogity' creatures. Anyone know where that name came from? 1000 points if you get it right! Anyway...the parasite would climb in its human victim's skull (forcefully of course) and push their eyes out and replace them with its own so it could see. It would then tap into their nervous system and control the host.