I knew someone who had a droopy-faced Basset Hound.
If I got that dog in an exited and playful mood, she would put out this incredibly hilarious smile. It was SOOO cute!
Dogs smile because a loyal dog has total love to their master. If their master is wise he knows the dog is their loyal companion and he is not a master but their loyal companion also.
Just tonight I had two of the most gentle and loyal dogs on my couch with me before I put them out for the night in their heated room for the night. They were 80 pounds of love each. If a bad person chose to attack me at first they would be confused for a few seconds. Once they determined it was a bad person, each would be 80 pounds of jaw and fury on a bad person.
Dogs are smart. My dogs do not even bother my two cats. They know they are part of the household. Sometimes they sleep together on their separate blankets but one foot apart.
I like my dogs.