Although this was not accidentally, I experienced something similar a couple of times and already wrote about that on another post.
I was Visiting an Urologist (Male, like 99,99% of Urologists in this country) at a Public Hospital. I was seeing him for a slight pain in one of my Testis. Dr made me lie on the table an low my jeans and Underwear below my knees. I did it and remained exposed like that while the Dr was at his Desk finishing writing some Notes and looking for some Rubber Gloves.
At that very moment the Office's door opens and in comes a moustached guy , probably mid 30s (I was 19) who was a Hospital Employee, that worked in the Staff of a small office in charge of assigning Appointments for the different Specialties' Drs (like Cardiology, Gynecology, etc) because their offices were located in that area of the Hospital.
He got in, greeted the Dr 'Good Morning' and went into the very small bathroom built inside that Office. The Dr didn't bat an eye as if it was a normal thing to break inside an office while a Patient is being examined!
He was about a minute in the bathroom, then flushed the Toilet and exited from it drying his hands with a paper towel and approached near the Desk and less than 2 feet away from me, while he chit chatted with the Dr about the Weather.
I was really surprised that he did that, but didn't attempt to cover at any moment, so he really got an eyeful of my Dick and Balls because the Dr hadn't started examining me yet. He was there for about a minute or two and then left.
The Dr examined me and prescribed some Pain killers and a Testis Ultrasound.
When I left Dr's office I saw this guy at his desk doing his Job with the rest of the Staff. Later on I've discovered that there was a Private Bathroom specially assigned for that office staff, located at the end of the Corridor, beside the Public Bathroom, but the one at Dr's office was the nearest for him (besides he probably got interesting sights whenever he went inside for using it!)