what happens in vegas 

Usually followed by 'stays in Vegas' - the details events of a weekend or short amount of time a person spent out of town are suppressed. The term would usually refer to someone going by themselves or with friends for a weekend in Las Vegas, Nevada, but you could apply it to another city/town if the other person knew what you were referring to.

"Whoa you twisted your pelvis while you're away? How did that happen"

"What happens in Vegas..."

what happens in vegas by mun-b April 16, 2008

what happens in Vegas stays in Vegas 

It happened. It only happened there. And it happened far enough away to have any negative effect on the "the here and now".
And anyone who wasn't there at the time need not know about it.
So stfu about it, and move on. But keep the memories. ;)

Dane Cook's intro to a recent show in Las Vegas:

"...great to be back here in Vegas....you know how they say 'what happens in Vegas stays in Vegas'....? Well I have a new saying....if it happens in Vegas, and I see it....I'm fuckin' telling EVERYBODY!!"

what happens in Vegas stays in Vegas by Mister B. November 18, 2006

What Happens In Vegas Stays In Vegas 

What Happens In Vegas, Stays In Vegas
('Cept Herpes, that shit stays with you for life)

Sarah: I can't remember, but I think I lost my v-card to someone last night in Vegas...

Best friend Nick, who was the one that she last her v-card to: Well honey, what happens in vegas stays in vegas. No worries.

What Happens In Vegas Stays In Vegas by AddictedToGrunge July 7, 2009