Helper dog is not amused

In my evening class there's a woman with a helper dog. It's a sweet doggy, but a bit mischievous at best. I thought they're not supposed to react to someone offering them something to eat, or lunge forward if you're nibbling at something.
And that's exactly what this four legged friend did. The blind lady was standing around drinking coffee with us during the break and I had brought a chocolate cookie with me. I always have a little snack to keep my brain going.
The dog started pulling away from her, wagging its tail and drooling while putting on its most beggarly mutt face. The dog's owner didn't know what was going on. So I had to explain to her I was eating a cookie. And then had to turn away so the dog couldn't see me anymore.

During the second half of the lesson, the dog wandered about a bit, then went and had a little sleep under our professor's desk. About half way we suddenly heard the most enormous moan. To everyone's amusement, it was the dog letting the teacher know to get on with his riveting explanation.