I had a dog who learned to smile. We simply asked him to "Show your teeth" and call his name. Then he would walk up to you and grin! it was hilarious. We knew that it was no coincidence because he did it at the same command. He was the only dog I ever saw do this. When he got old and loss a couple of teeth, he still did it, gums and all!
Another trick he would did was shake our hands at the command, "Give me 5". He did quite a few tricks, but those were my favorite.
RE: Doggy Tricks 
it was hilarious. We knew that it was no coincidence because he did it at the same command. He was the only dog I ever saw do this. When he got old and loss a couple of teeth, he still did it, gums and all! 
