Not a Three Dog Night, because, of course, there are only two of us.
Three Dog Night
It refers to being cold. Often when ranchers or cowboys were out on the range they would have to sleep with their dogs to keep warm. A one dog night was a night when he had to share body heat with one dog, two dog night was two dogs and a three dog night was an extremely cold night where he would have to share body heat with three dogs. “how cold was it on your trip?” “It was a three dog night”.
Mom pulled the covers back on PlusOne yesterday morning to find Lucky stretched out against PlusOne's back and me curled up against his stomach. I think that is what you call a win win situation.