let it happen

Usually said after a night of shenanigans or during a severely awkward moment.

"Just let it happen guys, just let it happen."

These things happen

A consolation offered to someone who has just experienced something shameful or embarrassing. This may be particular to Northern Ireland but I cannot confirm.

Seems common place amongst traditional working class families, a type of "stiff upper lip" attitude.

"Awhk Billy, you've never been done for drink driving before."
"Awh a'know but I'm just so embarrassed about it."
"Louk', these things happen."

Didn't Happen

A phrase commonly use when an event is brought up that was thought to be real, but did not occur.

Ryan: Hey john, we were talking about the H...
John: No no no, it didn't happen

what happened?

smartass comment used when one slips up or makes a mistake, or rips ass, and gets called out on it.

Jake - rips ass
John - Dude that smells like sewage!
Jake "What happened?!"

what happened?

Non-sensical, over-used replacement for "could you please repeat that?" Generally uttered by white males in the 12-16 year-old demographic. Enhances one's ability to sound like a moron.

Roger: "Hey, Joe, what time is it?"
Joe: "What happened?"

Not. Going. To happen.

Something you tell a guy when it's just NOT GONNA HAPPEN. Must be said in a high volume or tone so that all parties within the unit know he's not getting any.

Girl: What are you doing over there... are you getting a CONDOM???
Boy: Ahhhh noooo, just grabbing my wallet... (as he reaches into roommate's nightstand drawer)
Girl: Not. Going. To happen.

that's happening for real

That's awesome, amazing, or downright sweet. Also used to say you agree with the statement or plan.

The sincere opposite of that's totally gonna happen.

Kid 1: "We just got some crazy imported Chinese fireworks, wanna blow them up with us?"
Kid 2: "What?! YES! That's happening for real!!"

Guy: "Damn, check out that girl's ass! That's happening for real!"