My 15-week old puppy, Rigby, is going out of control! When my wife is sitting on the floor to play with him, he constantly grabs her wrist (with a good grip too) and starts the "humping" motion. She pushes him aside gently and he does it again. We say "no!" very sternly but he thinks we're playing with him! Does anyone know an effective way to discipline these annoying actions? When our neighbor's kids stopped by this past weekend, he did the same thing when they were just trying to pet him. It's really embarrassing!