On my flights from Asia to the United States we often enter  U.S. airspace near Seattle. On a recent ocean crossing we were switched from Vancouver (Canada) ATC to the Seattle ATC controller as we crossed our northern border. I change frequencies and then pause before making my radio call just in case there is a conversation in progress between the controller and another aircraft. In this instance I came upon a conversation between the Seattle controller and what sounded like a small plane near Klamath Falls, OR. It peaked my interest when the controller told the other pilot that she was trying to find out why he wasn’t following the clearance that he had been given.