Everyone that matters was in Vegas this weekend. Britney Spears, the Kardashians, and even the entire Jolie-Pitt clan. Of course the world’s most famous family of eight had nothing to do with Spears, though it would have been kinda funny if they’d all trekked in for her engagement party.

Alas, they had their own plans: celebrating Brad’s birthday at the at Cirque Du Soleil’s “Michael Jackson: The Immortal World Tour” at Mandalay Bay. Pitt turned the big 48… that’s right, only two years before he’s the hottest 50-year-old on the planet.

According to reports, Brad, Angelina, and the kids had awesome seats but otherwise didn’t make their presence known, and the cast didn’t know they were in the audience until the end. Probably for the best. When it was all over the Jolie-Pitts quietly ducked out and headed back to the Four Seasons.