Michael Jackson was busy putting on the final touches for his 50-date London concerts at the O2 Arena when he unexpectedly died. Now, ET's Thea Andrews is with the men behind the massive production to reveal what could have been Michael's most incredible concert tour yet!

A show filled with music, dance, stunts and pyrotechnics, Michael's "This is It" concert was being directed by Kenny Ortega, the man who designed Michael's "Dangerous" tour, choreographed 'Dirty Dancing' and also brought "High School Musical" to the world. Kenny says that Michael promised "the concert of a lifetime" and was prepared to deliver.

"We [had] some fun things planned," he says, referring to gigantic spiders, 20-foot puppets, a flaming bed, a pole dancing aerialist, a 3D movie and plenty more magic. "It's complex in scale and it's as big as anything I've ever done or attempted to do for an arena production."

Michael was reportedly planning to open the show with "Wanna Be Startin' Somethin'" and a glass sphere would float around the King of Pop, light up, drift over the crowd and then return to his palm.

Rehearsals for the concert series began at CenterStaging in Burbank, CA, owned by Johnny Caswell, but the huge space still wasn't big enough for the production, so Michael moved to L.A.'s Staples Center downtown.

"He was intently involved in making this, along with Kenny, the greatest thing he'd ever done," says Caswell, who adds that the performance stage, just under 10,000 square feet, "was not big enough to house the set, or high enough. It was really gonna be big stuff."

The "This is It" concerts will never be, but there are reports that AEG Live, the promoters, have approximately 100 hours of rehearsal video and may turn the footage into anything from a CD to a DVD, motion picture, pay-per-view or television event.

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