In this photo Charlee looks more like a Halloween cat than a dog.

I posted this photo a few days back and asked you all to tell me what Charlee's body language was saying.

The dog is clearly uncomfortable and she has piloerectus. Now you all go wash your brains out with soap! While piloerectus is a funny word, it just means that her that her fur is sticking up. Fur sticking up is not always a sign of aggression, although it sure can be. It is the human equivalent of human skin prickles, but if I didn't know Charlee and came upon her, I would not get close.
Dogs use piloerectus to make themselves appear bigger and therefor more of a threat. Notice her tail is up and over her back like a warning flag. In this photo Charlee has puffed herself up all the way down to the base of her tail, to send a message to Chase the foster dog that she was not comfortable with him and he needs to stay away.

If you looked at the photo and thought Charlee wanted to play, and you own dogs, I strongly suggest you buy your own copy of Brenda Aloff's excellent book CANINE BODY LANGUAGE, A PHOTOGRAPHIC GUIDE

If you took your up to a dog that was presenting a posture like the one Charlee is sporting in the photograph, there is a good chance that a fight would ensue. In this case, the foster dog had attacked her the day before and she was using her body language to clearly tell him to back off.

In this photo taken only 1 week later, Charlee is relaxed.

See the difference?