My grey tabby, Spicey, is 3 years old and on occasion, without warning, he will do the strangest thing. I am always standing when he does this -- he'll come up to me, stand on his hind legs, wrap the front legs around my thigh and bite me. It's not a hard bite, more of a love bite. Also, after coming home I always hold him and he rubs against me, especially my face. As he's rubbing his face against mine he will bite my forehead, again it's not a hard bite, and he's purring the whole time. I've always been curious about this.