Pixie, as a rule, is usually unfriendly towards strangers. I'll admit to not socializing her as well as I did with Tuffy but even so she dislikes people she doesn't know. Everytime we go out she will growl at strangers or hide behind me. She also HATES to be held by strangers (which is fine by me, I don't want them holding her anyways) and she doesn't like to be petted either. But once she gets to know a person she'll ease up and be friendlier. Tuffy, on the other hand, would go home with anyone who gave him a pat on the head.
