When Lucy Goes Out Walking by Ashley Wolff
My Kindergarteners love this book. We usually sing it in January, and it helps them remember the months of the year they learned in their classrooms earlier in the school year. By reading the book jacket, you learn that Lucy was a real dog, and the author has a blog. http://ashleywolff.com/wordpress/
I always teach the song first, then we read the book and sing the song on each page turn.
Some of my students will notice that through the year, in the illustrations, Lucy grows. So, we always go back and look at her picture in January, and compare it to her picture in December.