Yes, that is right. I do like to change parts of my body at various times, more in a joking kind of way, but it requires me to concentrate.. Mostly it's just my tail that will appear to poke you on the shoulder before it dissapears. I can change, and cannot control the change if I am extremely angry.
I am human infront of the eye, though my fire can sometimes i can lose control of my fire if I'm extreme passionate about something, happy / angry etc.
Also that senerio sounds fine with me