By lunchtime Thursday, Jackson was in cardiac arrest. But in the Staples Center spotlight, he was in high spirits and engaged, according to several collaborators. Energetic, optimistic and focused, Jackson gave no indication of what was to come, they said.
The show's director, Kenny Ortega -- a journeyman choreographer and movie director whose career highlights include "High School Musical," the "Hannah Montana/Miley Cyrus: Best of Both Worlds Concert Tour" and "Dirty Dancing" -- began work with Jackson on the intricate staging four months ago. On Thursday, Ortega recalled Jackson as bursting with enthusiasm and personally invested in the production's most minute details.
"There were a couple of times when Michael stood at my side and we looked at the stage together and were just beaming with gladness that we had arrived at this place," Ortega said. "And he was happy."
Ortega said he had no knowledge of the singer's taking any drugs or medication. He also denied that Jackson had overextended himself by working out four hours a day, six days a week in preparation for the tour.
"He was dancing, training, working every day with our choreographer Travis [Payne]," Ortega said. "Michael has always been slight. That was his fighting weight. He was getting rest time, coming in and working with the band, guiding the singers, working on orchestrations. He was enthusiastically involved in every creative aspect of this production."
Randy Phillips, chief executive of AEG Live, the concert promoter that will forfeit the more than $20 million it put into staging Jackson's comeback, was also at Staples on Wednesday. He recalled Jackson being in ebullient spirits.
"It was fantastic, he was so great. I got goose bumps," Phillips said. "It made me realize why I got into this business.
"I take great solace in the pride and confidence he exhibited during production rehearsals on Wednesday night. That is the memory I will cherish for the rest of my life," Phillips said.
Ken Ehrlich, the longtime executive producer of the Grammy Awards who staged televised performances by Jackson half a dozen times, met with the performer at Staples on Wednesday to discuss a television project. "He was very warm and funny. He was having a good time," Ehrlich said.
After the meeting, the singer invited Ehrlich to stay and watch him rehearse.
The show was still a work in progress, with props that Ehrlich recalled as "looking pretty magical" strewn about the venue's floor.
"What I saw that night was a person who was still in the process of learning the show," Ehrlich said. "I watched Kenny Ortega walk him through some stage directions. I know [Michael's] method, and there's a certain reticence when he's not in full make-up and wardrobe to 'give it.' He would have been ready by the time he got to London."
Ehrlich said Jackson showed his pervasive influence: "The hair on the back of my neck stood up. I wasn't watching Justin Timberlake or Chris Brown or Usher or any of the hundreds of acts that have taken from Michael. The modern inheritors of his art. It was him."
Jackson hired Ed Alonzo -- a concert magician-comedian known as "the Misfit of Magic," who also worked on Britney Spears' "Circus" tour -- to create two set-piece illusions for his London shows. One illusion set to the opening number involved an illuminated sphere that would have floated around the singer's body, flown out above the audience and then landed back in Jackson's hand before immolating in a blaze of light.
Alonzo recalled that the singer arrived at Staples around 6:30 p.m. Wednesday but did not begin rehearsing until 9, complaining -- perhaps facetiously, the magician said -- of laryngitis.
"He looked great and had great energy. He wasn't singing at full level, but it was as beautiful as ever," Alonzo said. "He went from one number to the other. 'Let's do that again.' He wanted to look at props for the 'Thriller' number, a gigantic spider. He was dancing, singing, joking with the crew. If he was having any aches or pains, nobody knew about it that night."
Frank DiLeo, Jackson's manager, said the singer seemed upbeat and ready for the challenges of mounting a comeback that he had hoped would restore his superstardom -- reinstating his cultural relevance, erasing part of his massive debt and finally allowing his three children to understand why fans worldwide herald him as the King of Pop.
"He just told me how happy he was and that things were working out the way he wanted," DiLeo said.