It's the show everyone has been talking about. So, of course, some celebs were bound to show up when Britney Spears performed her first show of her two-year stint in Vegas.
But what do you wear to a pretty cool concert - Britney's Piece of Me show? Hmmm, it's a difficult question. Katy Perry opted for what can only be described as a fairly odd and shiny American football shirt thing. She combined her top with a tutu and some knee high socks.
Wrecking Ball singer Miley Cyrus on the other hand went for a revealing little ensemble (what else would we expect?!) If that skirt was any higher it would have been x-rated.
Mario Lopez, of Saved by the Bell fame (and the American version of the X Factor), was also at the show, as well as actress Ivana Millicevic who was looking pretty fab in a monochrome ensemble. She pitched up in a white top with a high-waisted black leather skirt.
After the big performance, Brits tweeted to say how amazing the show was and included a sneaky peek of one of her outfits.