Sixty-two dancers. One week of cast rehearsals. Ncuti Gatwa didn’t arrive until Friday. Slash showed up Saturday.

“I’m Just Ken” was the showstopping number of Sunday’s Oscar telecast, and it probably wouldn’t have come together in as seamless a fashion if not for choreographer Mandy Moore, who has designed dance sequences for a Taylor Swift world tour and a film musical.

“Um, it was definitely up there with ‘La La Land’ and the Eras Tour,” she said when asked about how “I’m Just Ken” ranked in terms of career challenges.

Expectations were high before the ceremony. There were reports that the backup Kens would be shirtless, and in an interview on the red carpet, Mark Ronson, who was up for an Oscar for the song along with Andrew Wyatt, promised an “absolutely bananas spectacle.”

Although the dancers were fully clothed (and a different “Barbie” song would win the Academy Award), Moore’s troupe did deliver on Ronson’s promise. It helped that her partner in crime through the whole endeavor was Ryan Gosling, Oscar-nominated for his role as Ken in “Barbie,” who not only eagerly donned the pink sequin suit but also sang live and had clear ideas about how the number should go.

In Moore’s telling, it was Gosling’s idea to start the song in the audience, sitting behind “Barbie” star Margot Robbie as the physical representation of being No. 2, which is the focus of the song. He also wanted Ronson and Wyatt, the musicians and lyricists behind the hit, incorporated into the number along with a group of dejected Kens sitting on stairs. Gosling also suggested jumping off the stage to involve the film’s director, Greta Gerwig; Robbie; and his fellow “Barbie” Oscar nominee America Ferrera in the action, too.

The idea of riffing on “Diamonds Are a Girl’s Best Friend,” from the Marilyn Monroe classic “Gentlemen Prefer Blondes,” was already being thrown around when Moore got involved. (Rather than have women carrying candelabras, as in that 1953 musical, men would be holding large candlesticks; they were referred to as the Kendleabras.) And adding a Busby Berkeley-style moment involving giant cutouts of Barbie’s face was both an homage to the “I’m Just Ken” number in the film, which was choreographed by Jennifer White, and is a style that has come back into vogue in recent years, Moore said.

“It’s always a reference. Every job I do, somebody wants to do Busby Berkeley,” Moore said, referring to the director and choreographer known for elaborate 1930s and ’40s musical numbers that involved complex geometric patterns.

“It is incredibly difficult to do, even in a film situation, because you have to have really clear marks, and you’ve got to practice it over and over. It’s militarylike,” Moore said. “So, you can imagine how hard it is to do on a live show.”

In the end, the troupe only worked with the cameras five times between Friday and Sunday and rehearsed it twice Sunday before the show began. Then there was the fact that the stage was circular, which added to the complexity. And the giant Barbie doll heads didn’t arrive until Thursday. “That was a really super-challenging part,” Moore said.

It was Gerwig, though, who wanted the entire audience in the Dolby auditorium up and dancing. Before the big number, a recorded video appeared inside the ballroom, urging those seated to shine their phone lights and sing along. According to Moore, on the first call with all involved, Gerwig said, “Really, my dream for this thing is just that everybody’s up and singing. That’s my only dream.”

Simu Liu, who played a Ken in the movie and joined Gosling onstage, said that from his vantage point, “this came together extremely quickly,” adding, “Mandy Moore is an excellent choreographer.”

When he first heard from Moore, he checked in with his fellow Kens from the movie, including Gatwa, Scott Evans and Kingsley Ben-Adir, who all decided to take part, although he admitted, “Nerves were running high,” and added, “There’s not many rooms that are more intimidating.”

After it was all over, he said, the Kens felt exhilarated: “Yes! I think we pulled it off.”

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