Book excerpt: “He’s Only Playing!” Why? Because as a dog behavior specialist, this is one of Sarah’s LEAST favorite expressions! “He’s Only Playing” is what people say when they have no clue what’s really going on with their dog when it meets another dog. It covers the good, the bad and the downright inappropriate: a multitude of doggie sins and rudeness. Everything from one dog placing his paws on another dog without invitation, to another sniffing underneath just too intently.