Ethically however, I don't think they are allowed to do this on purpose or at least without your permission because it creates a dual relationship, so I believe he client does have say in this matter. If it were me, I'd most likely say no. I 'm self conscious however so I would feel put on the spot. If I had more confidence it might not matter to me.

I did an assignment with my pdoc once where we did a mock therapy session to create a Client/t dialogue for a class project. He offered to be the client - which probably would have been more interesting - but I was so scared about being judged in a "professional" role that I opted to remain the client.