Our Egyptian Mau came crying to our door one day about 18 months ago. Someone had either lost him (he had a collar, but no chip) or abandoned him. Vet estimated him at about 8 yrs old at the time, slight case of osteoporosis (previous owner probably fed him dog food at times - he's clearly accustomed to dogs bossing him around) and severe need for extensive dental work.
He almost always sleeps on his tummy. This very rare photo of him sleeping on his back was taken by our cat sitter while we were away. Definitely shows that cats can indeed smile!