Once upon a time it was hip, chic and witty but like all new phrases, it's surely had its day.
I refer to 'who knew?' which is the fashionable replacement for 'guess what?' or 'fancy that!'
Sometimes 'who knew?' precedes the boring fact which the speaker is about to share with us as in:
"Who knew? Housework is good for your health?"
More commonly, it follows the boring bit -
"Wine tastes even better with chocolate. Who knew?"
The words have spawned a series of 'Who Knew?' books. There is also a 'Who Knew?' news trivia programme.
I can't swear to this but the likely origin of the phrase is from the lyrics of the Pink song of that name - so American then. Who knew?
Anyway, be warned, if you see the words 'who knew?' you can be sure that you are about to read something boring and dull.
Oh - with the exception of this little jotting of mine of course.