This is kind of a backwards anecdote to tell in this thread for a number of reasons. But anyway…
When I was in my late teens my then gf and I went over to a female friend’s parent’s house (we’ll call her “the Blonde”). The Blonde had a pretty straitlaced upbringing but was at the time coming out of her shell. She had (has) an extremely high IQ but could be somehow amazingly dumb and naive at the same time.
So gf and I get let into the house by the mother of the Blonde who tells us that the Blonde and this male friend of ours (who we will call “the Guy”) were in the downstairs living room and we should just make our own way down. This was not unexpected as we knew that the Blonde was in serious flirtation with if not having it off with the Guy, despite him being, at least in theory, in a serious relationship with someone else. We knew this but it was theoretically a secret. So we opened the door at the top of the stairs and marched down. With the benefit of hindsight, there were perhaps some sounds of frantic activity in the few seconds available between us opening the door and us getting down the stairs, but at the time we didn’t notice.
By the time we got down the stairs the Guy was sitting at the piano looking as cool and nonchalant as he always did, and the Blonde was standing nearby blushing slightly. She excused herself shortly afterwards and went into her room (which came off the downstairs living room), and came back a few moments later looking more comfortable. She was wearing a very short dress.
The Guy left shortly afterwards. The Blonde looked embarrassed but blurted out:
Blonde: “Hey, you know when you guys came in here before?”
Us: “Yeah, sure”
Blonde: “I know what it looked like, but, ummm, there was nothing actually, you know, going on. And I was actually wearing knickers.”
Us: “Ahhhh… why would we have thought you weren’t wearing knickers? And we had no idea there was anything “going on””
Blonde: “Oh. Damn. So you didn’t actually notice…”
Us [laughing]: “You silly cow, we had no idea you were having a romp or lacking underwear till you just said that! You were having it off with the Guy when we came in here, weren’t you, admit it.” [Chortle, chortle, chortle]
Blonde: “Dammit, dammit dammit…”