I don’t think I’ve ever seen dogs, cats and other domestic animals smile because they’re happy and show love to their owners for treating them right.

My dog “smarls” (smile+snarl) at me when I come home. We’ve taken a still photo of him while smarling and it looks horrifically vicious. It’s like a stock photo captioned “aggressive dog”. But he’s actually happy. The difference is body movement. An aggressive or dangerous dog will be very still, just showing teeth, usually growling and backs away from a threat or quickly lunge if it gets too close. A smarl is usually accompanied by a wagging tail and body wiggles and slowly approaching to get pet.