I'm not going to lie to you and say I don't love this poem MAINLY because it's about a dog. I do. That's who I am. What's great about it for teaching, though, is the rich description and the way she captures this dog's character so perfectly with limited use of words. This is a great poem for visualizing and talking about "show don't tell" in students' writing.
And if you're like me, you'll weep a little before moving on to the next part of the book.