you know something

(Do you) know something?

Used to emphasize the importance or severity of the point being made. You know something? I'm sick and tired of your crappy attitude! So one day I simply up and left him, and do you know something? It was the best decision I've ever made. Know something? These layoffs are just the beginning. Things are going to get a whole lot worse.
See also: know
Farlex Dictionary of Idioms.

you know something

Also, you know what? Listen to what I'm going to tell you, as in You know something? He's always hated spicy food, or You know what? They're not getting married after all. Both these colloquial expressions are shortenings (Of Do you know something? or Do you know what?) and are used to emphasize the following statement or to introduce a surprising fact or comment. The first dates from the mid-1900s. The variant, from the late 1800s, should not be confused with what do you know or you know .
See also: know, something
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • (Do you) know something?
  • throw (someone or something) out of (something or some place)
  • throw out
  • throw out of
  • if ever there was
  • if ever there was (something)
  • no fox given
  • make much of
  • make much of (someone or something)
  • make much of somebody/something
References in periodicals archive
"I feel like it's your fault if you know something might happen to that dog and you don't do something."
It's possible you know something I don't, but I've always had the impression of her and the New Alliance Party as accepting money from gays and lesbians but not doing a whole lot to give back.
"If you know something's missing, touch base with the borrower.
Conclusion: Appealing and easy to read once you know something about JavaScript, but no beginner's book.
You can't put your finger on it, but you know something bad's going to happen.
And you know something? I decided a long time ago that it is worth it.