Mine does that sometimes as part of the morning routine. He waits for me to wake up, and when I do show signs of stirring, he'll remind me that it's time for his breakfast by miaowing and pawing at the edge of the bed. If I ignore him enough, he'll let me snooze for a bit, but when my feet touch the floor, he'll be rubbing up against and around my legs. If I'm not up quick enough, there'll be a light nibbling of my shins.
Taken to extremes, do you remember the story of the French woman who had the face transplant? Her dog bit her face to wake her up when she'd taken an overdose.