Weird Teacher Behaviour

15-yr-old girl I teach at home also has lessons at school.  With someone I know.  This has been rather amusing for me.  At the very start of her lesson, not even unpacked, she starts with this.

Girl: OH!  Okay, today, something very weird happened.
Me: Oh no!  M [her younger sister] just started her lesson almost the same way.  Is your violin okay?
Girl: Oh yeah.  Ha!  Yeah it's fine.  Okay, well, Mr P, at lunchtime today, we could see him just ... walking... up and down... like this [she walked a couple of metres, her arms flapping gently like wings]
Me: Why... was he doing that?
Girl: I have no idea.  But it was really weird.
Me: Did you ask him why?
Girl: No.  My friend and I were on level 2, and he was on level 1, so he was, like, a long way - a long way - away.  I only saw this because my friend saw him, and said, hey C, you have to see this... So, could you please ask him why he was flapping like a bird at lunchtime today?
Me: Um, sure.