The former pop power couple did not take the stage together, and it wasn't clear if they'd crossed paths.
Rumors of the guest appearances swirled Thursday, making it a can't-miss event for some of Hollywood's biggest stars: Elizabeth Banks, Drew Barrymore, Jennifer Lopez and Lucy Lui were among those in the first few rows.
Madonna took a moment from her turn onstage to lament the passage of a gay-marriage ban in California.
"I am the luckiest girl in the world," Madonna said, "but am sad because African-Americans are equal finally, but gay marriage is not."