NEW YORK - Two of the most powerful women in entertainment and fashion teamed up to throw a party in New York City.

Oprah Winfrey and Vogue editor-in-chief Anna Wintour, and Gap creative director Patrick Robinson co-chaired the annual Metropolitan Museum of Art's Costume Institute Gala Benefit on Monday night in New York.

This year's theme celebrated the American woman.

Stars like Justin Timberlake, Taylor Swift, Sarah Jessica Parker and Jennifer Lopez were there. Many were accompanied by the designer who dressed them.

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.

"Harry Potter" actress Emma Watson took a break from studying for her final exams at Brown University to attend, wearing a white custom gown by Burberry.

"I'm pretty lucky I get the best of both worlds and that's why I'm so blessed," the teenager said.

When asked what goes on inside the Met Gala, Anna Wintour responded with a laugh, "Oh, we're very, very well behaved."

Lady Gaga was slated to perform at the ball but didn't walk the red carpet. Instead, the famous face with the most unusual dress was singer Katy Perry. She wore a dress that literally lit up with LED lights.

"I feel like I really have to represent those girls that just go for it and do their own thing and, you know, have their own bit of spontaneity and self confidence," Perry said. "I think sometimes in fashion it can get a little stuffy so I wanted to lighten up!"