Runway falls at Opening Ceremony, Monks at Prabal Gurung

NEW YORK (AP) — It's every designer and model's worst nightmare: To trip while walking the runway during fashion week. That's exactly what happened, over and over, on Sunday evening at Opening Ceremony's show. The audience gasped as the first model took a tumble, but by the time the third "model" fell, most realized the stumbles were actually calculated. You see, some of the models were not models at all, but rather New York City Ballet dancers.

"This was to challenge the idea of the runway show and runway stride of models. It's an idea of not always trying to catch up and not being afraid to make mistakes," designer Humberto Leon said.

"They always got back into their place. It's an idea of making it about how these girls do it. ... It's celebrating mistakes in life."

The collaboration is fitting considering the label is designing costumes for the ballet. Resident choreographer Justin Peck even choreographed the dance for their runway show.

So, was Leon concerned the theatrics would make the audience, which included Kylie Jenner and boyfriend Tyga, Laverne Cox and Jessica Alba, focus on just the dancing and not the clothes?

Not a chance. "The audience was a part of this," Leon said. "We wanted the participation of the audience. You didn't know if they were falling. This is a cross conversation of life. We got to share this special thing I've been working on this audience."