Ran into a friend who happened to have his dog in the car along with a couple of kids. The dog seemed friendly and climbed up on the drivers lap (owner). Tail was wagging and had that "happy" look. I asked if he was friendly and could I pet him and he "sure, no problem". Petted him and all was well. Hubby, who had been standing beside me, reached over to give him a pat and the dog showed his teeth and lunged. The owner was surprised and said that's never happened. Hubby "talked" to the dog, dog wagging his tail looking really happy, so hubby took one baby step closer and the dog lunged again. Never assume how a dog will react!