Designer Oscar de la Renta with Oprah Winfrey, one of the hosts of the Costume Institute Gala at the Metropolitan Museum of Art

*Lady Gaga reportedly had her entourage panicking at Monday’s annual Costume Institute Gala in New York after locking herself in the dressing room and refusing to come out – that is until event host Oprah Winfrey knocked on the door.

According to the New York Post, the singer had been personally asked by Vogue editor Anna Wintour – who throws the lavish bash at the Metropolitan Museum of Art every year – to perform for the star-studded crowd as the featured entertainer. But for some reason, Gaga wasn’t prepared to take the stage and reportedly locked herself in the changing area.

“She literally wouldn’t come out. Friends tried, (Warner Music executive) Lyor Cohen tried, no dice (luck). Eventually, (artist) Vito Schnabel came over and got (Gaga’s friend) Terence Koh on the phone to talk to her, which helped. Koh and Oprah were the ones who finally coaxed her out.”

Gaga eventually took the stage – but with an attitude. She told the A-list audience Wintour had requested she refrained from swearing onstage, adding: “So Anna, I will do my f**cking best!”

Lady Gaga performs at the Costume Institute Gala

Lady Gaga performs at the Costume Institute Gala

The theme of this year’s Costume Institute exhibition was “American Woman: Fashioning a National Identity.”  Organized by the curator Andrew Bolton, the show looked at styles between 1890 and the 1940s, relying on exceptional pieces from the Brooklyn Museum’s collection like Worth gowns, gray walking suits and bicycling outfits.

Stars like Naomi Campbell, Zoe Saldana, Usher, Rosario Dawson and Jennifer Lopez were there. Many were accompanied by the designer who dressed them. [Scroll down to view photos.]

Winfrey walked the arrival line with Oscar de la Renta, wearing a navy couture gown by the designer. She said she looked forward to going into the party and having a few shots of tequila.

Mary J. Blige

Naomi Campbell

Zoe Saldana

Chanel Iman