At first Adamson wanted to use actors in the key roles, "but I also knew that I wanted to end with some kind of beautiful romantic straps aerial act."

"To teach a normal person to do (aerial) straps, to perform at this level takes years," says executive producer Jacques Méthé of Cirque du Soleil. "The way to go was to take Cirque du Soleil performers and teach them to play the part. At the end of this film, they are both flying in each others' arms. They need the skills and training of a real Cirque du Soleil performer. Igor and Erica have worked on several of our shows for years. They are not only wonderful acrobats, but because of their Cirque du Soleil training, they have learned to become characters. In any Cirque du Soleil show, everybody is a character and plays some part. So we knew these two had the acting skills because of their years with Cirque du Soleil."

Erica Kathleen Linz was 19 when she joined Cirque du Soleil shortly after graduating from high school. "I grew up as a gymnast and a singer, which led to theater, so I have flip-flopped between acting and acrobatic roles, and recently I've been doing an aerial straps duet which fits into this whole theme," Linz says. Landing the film role gave her an opportunity within Cirque du Soleil that she had never known before. "There's never really been an opportunity for anybody to kind of float through the shows, participate in what they do every night and get a feel for each show's culture. Every show is sort of like its own family, has its own vibe, its own set of nationalities and sense of humor. Personally, it's been unbelievable for me."

Although she and co-star Igor Zaripov have performed in the show KÀ, neither performed a duet together before Cirque du Soleil Worlds Away. Zaripov, who joined Cirque du Soleil in 2002, grew up in a Russian circus family that had been in the business for more than a century. He has been an aerial acts acrobat from his first stage appearance at 11 for the Moscow Circus. He traveled with other circuses around the world honing his skills. When he joined Cirque du Soleil, he performed in KÀ for five years as the Firefly boy and in Cirque du Soleil's adult-themed Zumanity for several years. "I had never worked closely with Erica before but we had to get into it really quick (the first time for the love scene of the final act) and it was really nice," he says.

What they do, although an outgrowth of KÀ, was created specifically for the film — a romantic aerial straps ballet which captures the ascendancy of love. "What you see is how these two learn to trust each other so completely. Her life is literally in his hands an act of total surrender," notes Cameron. "The acting is inferred by the physicality of the moment. And the grace with which it is done is simply beautiful."