This happened to me about 6 months ago. I am a 50 year old male that occasionally enjoys wearing women's panties.
On this particular day I was wearing a pair of casual dress pants and a polo shirt. Under I was wearing a pair of my wife's panties, a pink thong. It had been keeping me rather excited throughout the day but it was almost time to go home. It was a little after 5 and I was straightening up my office when Karen popped in and asked if I would give her a hand.
Karen was moving her desk and needed a little help. As we were doing this Jennifer came in to observe the goings on. We got the desk in position but some cords needed to be routed under the desk. I got down on the floor and was reaching back under the desk straightening and connecting cords. I could hear the women whispering but couldn't make out what they were saying. I was totally oblivious to the fact that my shirt had ridden up exposing the top of my pink thong.
Karen is 55 and pleasantly plump but rather average looking. Jennifer is close to 60 and a little plumper but somewhat attractive for a plump woman. They are both about 5'5", dress conservative but stylishly. Sex was never much of a topic of conversation so I never really knew of their views of sex. Prior to that day I would have assumed they were rather prudish.
It a small office and being after 5 it had emptied out. As I back out from under the desk and stood up the women where giggling to each other and I ask them what was so funny. At that point Karen shut the door. Karen being the bolder of the two asked if I was wearing a woman's thong. At which point I turned beet red and I said you can't tell anyone. They looked at each and Jennifer said I don't know. I said I will do anything if you promise to keep it a secret. Karen looked at Jennifer and said I think we should make him show us his panties. Then they both looked to me and said "we want to see your panties". All flustered I didn't know what to do but I managed to say "you want me to get undressed". Karen said yes that's the idea, we want to see you in your panties.