Part of being a violin teacher is the need to keep some sort of composure during whatever comes up in the lesson. I am very self-conscious of my response to musical problems---I constantly anticipate, analyze, and adjust my tone to give the best feedback to the student.
But I don't feel too solemn when they do things like, show up in a bikini asking for a bandaid for her owie knee, reply to all directions in a squeaky voice, topple over backwards at random, have gas, say, "my legs hurt," and "I have to go to the bathroom." I usually laugh, and do my best to accommodate.
As I said, I concentrate so hard on their technique, musicality, and practicing habits, that I really enjoy the comic relief! As my 2-year-old likes to say, "That was silly!"