[F 28] I have a different kind of "embarrassing moment" to share. Several years ago I took a new job as an attorney which required a physical exam for life insurance purposes. I was hired at about the same time as another attorney, a cute guy name Nick from my law school class. The firm administrator made the appointments for the life insurance physicals and for convenience scheduled mine at the same time as Nicks. It seem fine with me. We even drove to the clinic together. 
The exam didn't take that long. Since it did not include a gynecological exam, the doctor indicated he would perform a rectal exam with me in the "knee-chest" position. I complied with the doctors' instructions and assumed basically a "doggie style" position on the exam table. The doctor lifted up my gown, exposing my bare ass which was sticking up in the air. Then he applied some lubricant to his glove and was about to stick his finger up my ass, when all of a sudden the door opened. I looked back between my legs and could see: It was Nick! 
Nick stood there for wait seemed like 10 seconds looking very confused, before he realized he was in the wrong room and turned around and left. I later learned that he had been told to go to the lab to provide a urine sample, and returned to the wrong room by mistake. He was extremely apologetic about the incident, and even though I've been told dozens of times that I have a "great ass," whenever I look at Nick I feel embarrassed realizing that here is a guy who has seen everything: including my butthole!