Pixel is a very bad kitty girl sometimes, so we do need to be firm with her. We usually yell "No!" loud enough to startle her and get her attention, and we also will stamp feet, clap hands or make another noise that is sharp enough to capture her attention. If necessary, we'll remove her from the room that she is in, or from the object she is destroying! We also use the waterbottle as a last resort as she just hates it!