We wish we had been there!!
Along with 25 of their friends, the two showed up at KA by Cirque du Soleil in a stretch Hummer convertible at the MGM Grand and later posed with the freakish cirque acts backstage.
After the show, the group headed to a top-secret location.
While in Vegas, Katy tweeted that she was "signing up for a liver transplant now…"
Seems like a wild night!! BTW, We love the "B" for Brand, Katy! Nice touch!
[Images via David Becker / Getty Images.]