The envelope-pushing pop superstar was one of several musicians who performed Saturday night at the Hollywood Bowl during a concert celebrating the 10th anniversary of Clinton’s foundation, which has sought to improve global health, strengthen economies worldwide, promote healthier childhoods and protect the environment for the past decade.

Emerging from atop an all-white treehouse, Lady Gaga sported a wavy blond hairdo and red lips like Marilyn Monroe, who famously crooned “Happy Birthday, Mr. President” to President John F. Kennedy in 1962. Lady Gaga similarly serenaded Clinton and changed several of her lyrics to reference him, including swapping the title of “Bad Romance” for “Bill Romance.”

“I thought, ‘My God. I get Lady Gaga, and I will have a heart attack celebrating my 65th birthday,” Clinton later said.

Clinton, who turned 65 on Aug. 19 but celebrated his birthday at a posh Hollywood party Friday night, sat between wife Hillary and daughter Chelsea in the front row throughout Saturday’s event at the outdoor venue set against the Hollywood Hills. Other famous attendees included Maria Bello, Ashton Kutcher, Jason Segel, Ellen DeGeneres, Colin Farrell and Chevy Chase.

“I am the only person in history who got to be President and then had a post-presidential birthday party attended by both Lady Gaga and the Secretary of State,” Clinton joked on stage. “I want to thank Hillary because we met 40 years ago this year. When I met her, she was already doing the kind of work you see here long before it was cool.”

Ticket prices for “A Decade of Difference: A Concert Celebrating 10 Years of the William J. Clinton Foundation,” which was streamed live on Yahoo.com, ranged from $50 to $550. Other performers included Motown legend Stevie Wonder, country star Kenny Chesney, Somali rapper K’Naan, Colombian crooner Juanes and R&B singer Usher.

Usher kicked off his performance with a take on Joe Cocker’s rendition of the Beatles classic “With a Little Help From My Friends” before launching into his hits “Yeah” and “OMG.” The R&B singer accidently split his pant legs while dancing to reveal his bare left leg. The wardrobe malfunction didn’t stop Usher, who continued with his routine, telling the crowd: “I work hard.”

Bono and The Edge of U2 closed the concert with a mostly acoustic set that included such tunes as “Desire,” “One” and “Sunday Bloody Sunday,” which Bono sang directly to Clinton. The duo -- who were accompanied by a string quartet and Edge’s laptop -- closed with “Miss Sarajevo.” Bono tackled the operatic part of the tune originally sung by the late Luciano Pavarotti.

Clinton himself is no stranger to performing. The saxophone-playing politician memorably belted out “Heartbreak Hotel” when he visited Arsenio Hall’s show during his 1992 presidential campaign. Clinton didn’t pick up the instrument Saturday night, despite a plea from Lady Gaga, who informed him: “I wish you were playing sax with me tonight, baby.”