No, Smile Dog is made up just like Slenderman and many other made up creatures. These creatures belong to a family called Creepypasta. Creepypasta includes many creatures and their horrifying stories. You can listen to stories on YouTube.com. I hope this helped!
It did! But I wanted to ask this because I saw one version of the pic, and got no nightmares, but the second time I pulled it up it took a while for me to see it( it was almost completely black) but then I started to see it. I don't why that happened, but I in a car on a sunny day, so maybe it's just normal.