Brad Pitt and Angelina Jolie got a jump on his birthday celebration by attending a performance of Michael Jackson THE IMMORTAL World Tour in Las Vegas on Saturday.

They were spotted in the audience at the Mandalay Bay Events Center, sitting in the second row with Maddox and Pax, Zahara and Shiloh. The family seemed to thoroughly enjoy the performance and stayed until the end, joining the crowd during the final standing ovation.

"The artists were thrilled by their surprise appearance," a source tells RadarOnline.com.

Pitt turns 48 today.

Happy birthday!