The dog had fleas!

There was a howling, yapping, yipping and very unhappy dog outside the supermarket...tied up just where I park the trusty trike. 
I eyed it off with caution. It came up to me with tail wagging as hard as it could go without actually falling off. A human! A human who might talk to me.
I looked carefully. Mmm...a male of the species. I looked him in the eye and, when he tried to jump up on me I said sternly, "Sit!"
He sat and put his head on one side. Hopeful? Anxious? 
"No, I am not your human," I said, "I am not taking you for a walk. Your behaviour is attracting the wrong sort of attention."
I locked the trike to the railing, took my things and moved off. There was another outraged and very unhappy noise. It was ear piercing, a high pitched yip, yip, yip.  How dare I leave him on his own!
So I looked back again and said, "Sit! Be quiet!"
He sat. He stopped yipping - at least for a moment.
Someone coming along looked at me and then at the dog.
"No, it isn't my dog," I said in self-defence.
"I thought it must be. I can't get our dog to do that!"
I went in through the glass sliding doors just as someone else was coming out. They gave me a slightly odd look.
Then, as I was no more than three metres inside the door a voice said,
     "Excuse me - how did you get my dog to do that?"
I looked back. It was the man who had given me the slightly odd look. 
     "I have no idea," I told him, "I just told him and expected he would do it."
     "Oh - well thanks anyway."
Now I might be wrong but it seems to me that the dog has managed to learn to sit on command - although I doubt it would stay quiet as it was anxious. The other thing was that yes, I expected he would do it if he knew what to do when I gave the command.  I wonder whether his owner actually expects the same thing? 
Some people would say it was not a good thing that the dog was obedient for me  - even if only momentarily. It bothers me more than a little that the only had apparently only managed to get part way with the training. I firmly believe that dogs, like children, are happier when they know what the boundaries are. (Cats are a different story. They self-regulate for the most part.)
But the unhappy animal got back at me anyway for not staying and providing comfort and reassurance. It had fleas - and I was bitten.