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By Kat Giantis

They've done the cozy tête-à-tête over cigarettes. And the footsy-filled lunch date a deux. And the make-out-inclusive whirlwind getaway.

Now, Scarlett Johansson and Sean Penn have taken another step forward in their head-scratching hookup by having the obligatory meet-up with friends.

People mag reports the pair, who reportedly began hanging out in January, didn't hide their affection while chowing down with pals on Saturday night at an Italian eatery in Los Angeles.

"They were all smiles all night and seemed to have a great time together," says an eagle-eyed observer. "Scarlett and Sean sat very closely and exchanged flirty looks."

And echoing previous reports that ScarJo, 26, who split from Ryan Reynolds in December, is smitten with the 50-year-old Oscar-winning do-gooder's "depth" and "sexy, college-professor" image, she apparently couldn't keep her eyes off him as he held court over wine and pasta.

"Scarlett acted very intrigued by him," opines the snitch. "She would smile, nod her head and just listen to his stories."

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Adds an eyewitness to E! Online, "They looked really happy together. They playfully touched each other a few times. They were really just laughing, and it seemed like they were having a lot of fun together."

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Yet another onlooker managed to make a sweeping generalization about Sean's feelings for Scarlett from their noshing session.

"They were definitely on a date -- these two are way more than just friends," the spy tells X17. "Sean is known to be a tough guy, but Scarlett seems to soften him. He's a boy in love when he's around her -- or at least a boy in lust."

But after dinner, it was the actress who appeared to take the romantic lead. They exited the restaurant and made a beeline for a waiting limo, where Scarlett kept her head down while situating herself comfortably atop Sean's lap.

Johansson's rep has previously said the two are just pals with a mutual interest in the plight of Haiti.

Meanwhile, as ScarJo and Sean seemingly heat up, the actor's ex-wife, Robin Wright, has cooled off with producer beau Greg Shapiro after about a year of togetherness, reports E!.

After a few unsuccessful false starts, Penn and Wright finalized their divorce in July 2010 after 20 years together. In January, he kvetched to the Hollywood Reporter about how he "got taken for one half of everything I had."

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