Lady Gaga, Miley Cyrus vie for attention at MTV's Video Music Awards

Miley Cyrus made Lady Gaga look surprisingly tame as the pop stars opened the MTV Video Music Awards.

Gaga changed costumes four times Sunday night during her first return to the stage since hip surgery as she performed her new single "Applause." It was a predictably unpredictable appearance for Gaga, who seemed to pump in boos over the sound system as she opened the song in a white nun's habit and square headdress. By the time she finished the song, she was surrounded by unitard-clad male dancers and wearing a long blonde wig and a thong bikini decorated in shells.

But it was Cyrus who stole the show. She immediately kicked things up well beyond provocative, appearing on stage with a multitude of dancing teddy bears in a bodysuit adorned with a cartoon character. She twerked, changed into a flesh-colored bikini, ran a fan's foam finger along her privates as Robin Thicke appeared on stage to perform "Blurred Lines," then gave the singer a lap dance. The wild child also slapped a girl's butt onstage.

"Miley better go get a pregnancy test after all that grinding," Kevin Hart joked afterward.

Twitterverse quickly exploded with reactions to Cyrus' racy moves.

Other users criticized the 20-year-old singer's barely-there clothes and super skinny figure. And her performance was shocking enough draw reactions from her fellow celebrities. A photo of Will Smith and his family looking appalled during Cyrus' performance went viral.

Brooke Shields, who played Cyrus' mom in a few episodes of "Hannah Montana" on the Disney Channel, took note of that on the "Today" show Monday: "I was Hannah Montana's mom! Where did I go wrong?"

Miley's real-life father, Billy Ray Cyrus, declined to comment on the controversial performance, his rep told FOX411.

Gaga and Cyrus were just the first of a cavalcade of music's top stars performing Sunday night at the Barclays Center in Brooklyn, where the awards were held for the first time. They managed to drown out rumors about the 'N Sync reunion temporarily and left Katy Perry, Drake, Kanye West and several others quite the spectacle to top.

The Associated Press contributed to this report.