Actually, I always feel kind of left amidst the mess of my friends and their friends. I am always kind of nervous around my friend's friends, and it might be because I know I have to see more of them. Also, if it's around a friend who is mine, I get even more nervous. I'm always feeling like my friend even thinks I'm weird, because they'll know how "normal" I can be, and all of a sudden I'm this anxious person unable to handle myself.
A lot of the times it even makes me a little jealous. My friends always become friends with each other. I always feel like I went through all that uncomfortable effort getting to know someone, and they all get something handed to them. Of course, I try not to think about that too much, or let it bother me.