Jermaine on what Michael was up to before his Motown 25 performance:

And then we didn’t see him. He just… disappeared. He must have been gone half an hour.

"Where you been?" I asked, when he came back to the dressing room. He started chuckling and that mischievous grin spread across his face. "Been up in Diana’s room… She’s got some serious suitcases going on!" he said.

"Wait, I’ve just seen Diana Ross - and you weren’t with her."

He looked at me. I looked at him, and we died laughing.

"You’ve been rooting through Diana’s stuff!"

So that was one part of the question answered. What was Michael like before the show? He was nosing about his mentor’s dressing room, wondering what she had in there.