I enjoy this one, but I've become a little conflicted on the whole "Oh, I can tell you're really awake, let me mess with you because you'd stop me if you really didn't like it" bit, largely because I've had some sleep paralysis lately — y'know, when you've just awoken but you can't move, because the brain switch that keeps you from moving during dreams gets stuck. Just makes the prospect a little sour.
(Sleep paralysis is also the physiological effect that's been considered to be behind such experiences as alien abductions, shadow people, hauntings, and succubi/night hags — there's some fascinating literature on it.)