Reddit shares their best cases of accidental nudity
 

Airport toilet.
 

One time when the toilets at an airport I go to a lot were being cleaned and I desperately needed a pee. Next to it was a toilet for the disabled that was unoccupied. I slid the door open to be greeted by a very startled young woman with her panties round one ankle and one foot on the rim of the toilet. In a flash my eyes automatically moved from her shocked face to her nether regions where I was greeted by the site of her inserting a tampon into her shaved pussy.

It turned out she was on our flight and as we stood in line we acted as if nothing happened. I never told my wife and I don't know whether she told her boyfriend/husband.

Nice :)