A Dog's Best Friend

Rooty likes to sit at the edge of the lake and bark. The sound travels over the water and echoes. Rooty thinks it is a dog barking back at him, so he barks back. He will just keep exchanging barks with the echo unless something else distracts him. It's something like the famous line from Pogo: 'We met found the enemy and he is us.' Rooty has found a friend somewhere out across the lake, and his friend is him.