Charlotte Nebres is the first black Marie, the young heroine of “George Balanchine’s The Nutcracker,” at New York City Ballet. It’s a milestone for the production, which dates to 1954.

"While I am dancing, I am very focused. I listen to the music and the lyrics. I also think about my movement: How can I dance beautifully? I actually forget that I am aging.”

Around 300 dancers — boys and girls, men and women — took turns glissading across the concrete at 44th Street and Seventh Avenue. Supporters held signs with messages like “#metutu,” “Boys Dance Too” and “I Wish I’d Started at 6!!!”

“Prince William says George absolutely loves ballet,” she said, looking mystified while she stifled laughter. “I have news for you, Prince William. We’ll see how long that lasts.”

“I realized at the beginning of last year that my future plans for the next three years included a majority of women,” Kevin McKenzie, the company’s artistic director, said in an interview. “I thought, we’re doing this anyway — why don’t we formalize it? It’s important to level the playing field, if you will, but what’s paramount above and beyond that is, Where is the next voice?” Mr. McKenzie said. “I’m looking for somebody who can ignite the excitement of where we are in time. I just care about the work. And it turns out that the work that is catching my eye seems to be a higher percentage of women.”

Ballet is slower to change than most art forms, but in the span of just two weeks, New York City Ballet, one of the world’s premier companies, will have shown two ballets featuring significant same-sex duets.