Can dogs smile? Google that question and you'll see an ongoing debate. Some say the "smiles" we see on our dogs' faces are just expressions that form when our dogs pant and stick out their tongues. If a dog's owner sees it, the dog usually gets a lot of positive attention so the behavior is repeated again in the future.
I don't believe it. I think Gracie smiles whenever she's very happy, like when we're playing fetch in the yard (see photo above).