Britney Spears and Justin Timberlake each took the stage in separate appearances at Madonna’s Sticky & Sweet tour at L.A.’s Dodger Stadium Thursday night.

But, PEOPLE has learned, the two actually crossed paths during rehearsal. Timberlake was first, and then Spears came on stage to run through her part. “They said ‘hi’ to each other. Justin was very cool,” a source says.

Adds another source, “This was a night for [Britney] to enjoy, and not stress over. This was a good moment for her to just enjoy and have fun.”

And enjoy she did. Dressed in satin black pants and white suit shirt with ruffle, Spears has been appearing in a taped segment during Madonna’s “Human Nature” performance since the beginning of the tour. Her “It’s Britney, b—-!” segment she did live.

Madonna greeted her with “Hi Britney!” And Spears, with her blonde hair flowing and red lips smiling, moved to the beat as she sang the last chorus on “Human Nature” with Madonna.

“She’s not your b—-” Madonna proclaimed, pointing at Spears who replied with her classic line: “It’s Britney, b—-!”

Madonna had to swing her around three times to get her to loosen up a little bit and, in a far cry from the 2003 smooch, kisses Spears on the hand as her platform sunk below the stage.

“4 Minutes” came on and remixed into “Vogue” as Spears disappeared from view.

Timberlake then joined Madonna to belt out their duet “4 Minutes.” Dressed in black pants, a black jacket and scarf he and Madonna really went at it, playing off two dancers, dancing and grinding on each other. The crowd loved it.

“It was great!” a fan told PEOPLE at the show. “They really kept each other going up there. And, wow, only Madonna could bring the two exes together!”

At the close of the concert, a photo of President-elect Barack Obama flashed on the screens as Madonna announced, “We have something to celebrate! I’m the happiest girl on the planet right now.”

She continued: “Sorry to hear we didn’t win on Prop 8, but don’t give up the fight. If we can have an African American in the White House then when we can have gay marriages.”

Madonna, who split from director Guy Ritchie last month, will wrap up the North American leg of her tour Nov. 30 in Mexico City.

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