When tickets for Michael Jackson’s This Is It went on sale on Sept. 27, hundreds of shows around the globe sold out in less than 24 hours, without anyone knowing quite what it even was — a concert movie? A documentary? “It’s somewhere in between,” says Sony Pictures co-chair Amy Pascal of the film, which consists of behind-the-scenes footage of Jackson rehearsing for his planned comeback concerts at London’s O2 arena. “It’s a movie about rehearsing for a concert that never happened. It’s heartbreaking and inspiring at the same time. It gives you chills.”

Now, with the October 28th worldwide release of the movie fast approaching, the late pop star’s collaborators open up about working with Jackson during his precarious last days. At age 50 Jackson hadn’t toured in more than a decade, but while his team worried at times about his health, his imagination was as active as ever.

In fact, as the production got under way, it quickly became clear that Jackson’s creative ambitions for the concerts were beyond anything he’d ever attempted. With the budget already past $24 million, Jackson told his team he wanted to recreate one of the world’s largest waterfalls — Victoria Falls in southern Africa — on the stage. “I was ready to jump off the balcony of my office,” says Randy Phillips, president of the concert promotion firm AEG Live. “We went and met with Michael, and [director] Kenny [Ortega] said, ‘Michael, you’ve got to stop. We’ve got an incredible show, we don’t need any more vignettes.’ Michael said, ‘But Kenny, God channels this through me at night. I can’t sleep because I’m so supercharged.’ Kenny said, ‘But Michael, we have to finish. Can’t God take a vacation?’ Without missing a beat, Michael said, ‘You don’t understand — if I’m not there to receive these ideas, God might give them to Prince.’ ”

For more on the upcoming Michael Jackson movie, including exclusive photos, pick up the new issue of Entertainment Weekly on stands Friday, October 16th