I was at my endocrinologist again about one year ago for a testosterone shot and I had already a 100% passing at that time and a 5-o'clock shade that day. My endo was on vacation, and a guy made the temporary replacement. I was sitting in the waiting room which was crammed with people. Then he called me in:
"Mrs XY, come in please"
I stood up and went through the room to enter the consultation room. The other patients looked completely confused when they saw me go there, and I felt embarrassed and my face got red, but I also had a hard time not to burst out laughing at the same time.
"Okay, Mrs. XY, sit down... so you want to become a man? But you know, madam, it's not that easy, you first need to go to therapy for a certain time to check whether you're transsexual, and we need your blood levels tested blabla..."
I grinned at him: "Yes, I know all that, been there done it. I have been getting testosterone shots in your doctor's praxis for two years now."
He went: "Oooops..."

and looked into my file. "Oh, rou're right... so I addressed you wrongly in the waiting room, sir... I'm very sorry for that." Then HIS face got red with embarrassement.
I grinned again and said: "Oh, it was embarrassing, but also very funny to see how much you confused your other patients by calling me Mrs, so don't worry. Yo're the temporary replacement, don't know me, have a horrible load of work so mistakes happen."
"I'm relieved that you take it that way.."
"Oh, humor is what helps me best dealing with being a transsexual, you know?"