Sometimes it seems that students want me to be their friend. Sure, I'm the cool sub. I wear vans, and have a pink peekaboo stripe in my hair. Plus I don't yell, too much anyway, and I try to reward students when they behave for me. Even though, I really need them to know that if they cross a line, joking too much, talking to their friends, etc, I'm not their friend. I'm the person there to make sure that they don't lose a day of learning because they're teacher is our sick or learning better ways of teaching them.
Sometimes it is hard for teachers to not feel a connection with students. Especially when you are a wandering teacher, like I am right now. Students who are friendly are a welcome from students who just try to push your buttons and see "how miserable we can make the sub."