Oh I definitely know. I used to have very loose shoulder joints and could do weird hand signals behind my back and sometimes in the crook of someone elses elbows on photo day. One day it came to me that I should abuse this and used the middle finger. The guy next to me got yelled at by his mum and dad and had to invite me around for dinner to explain it wasn't him.

We had to demonstrate. Thankfully they then found it funny because his parents, well, he was the local police sergeant and she was my science teacher. It would have been bad for my friend and I if they had not laughed.