Since I occasionally play rough with Billy (I like to rub his tummy, which he usually doesn't think much of), Katherine is amazed I still have all my fingers. He puts up with it because a) his brother does worse to him, and b) I make it up to him with kitty treats or by picking him up and boosting him to the magic shelf used to store the feathers. (Billy especially likes this because after he sniffs at the toys, I take one down and use it to play with him.)
I didn't play rough this morning, but I did play stupid. In the midst of teasing him with the feline feather duster (especially waving it in his blind spots), I went to pet him. Billy assumed this was another pass by the duster, and as fast as he could twisted and bit the evil attacker, which was actually my thumb.
However, he didn't bite as hard as he could. He didn't even break the skin.