As a host of stars stock up on oodles of luxury freebies at the Sundance Film Festival, two big names are doing their best to give back. Over the weekend, Scarlett Johansson was a weapon of mass distraction as she turned many a marine into mush during a trip to the Persian Gulf, while David Beckham met some young fans while bringing attention to the crisis in Sierra Leone.

Let's start with the sublime starlet, who teamed up with the USO for a five-day tour that saw her visit with several hundred (mostly male and beaming) members of the military.

"It's important to give people a piece of home and to boost morale," explained Johansson during a pit stop at Camp Buehring in Kuwait (via the Marines Corps News). "Everybody out here is risking everything, giving us one of the biggest gifts they can. I want to be out here to support them."

Scarlett signs an officer's uniform patch.

The actress, looking very '50s pinup in a simple pink sweater, ponytail and bold red lipstick, took her duties seriously, shaking every hand, posing for photo after photo and signing her name to whatever was offered, even uniform patches. (Check out video of her morale-boosting here.)

One starstruck and surprisingly golden-throated member of the oh-so-charmed forces even serenaded Scarlett, who rewarded his efforts with a hug and a peck on the cheek.

"It's nice to give them a smile in the middle of the day," she enthused. "If they are missing home, feeling down or worried, hopefully being here will get their minds off of things."

Judging by the ah-oohga!-like looks on some of the soldiers' faces, Johansson, who earlier this week denied a report she was engaged to boyfriend Ryan Reynolds, more than accomplished her mission.

Meanwhile, UNICEF goodwill ambassador Beckham just spent several days in Sierra Leone in an attempt to shine a light on the plight of the African nation's most vulnerable citizens.

"We can't turn a blind eye to the tens of thousands of young children who die every day in the developing world mostly from causes that are preventable," the soccer star -- and dad of three -- said in a statement. "In Sierra Leone, one in four children dies before reaching their fifth birthday."

Declared Beckham, who got hands-on during his visit by administering polio vaccine to a newborn, "It's shocking and tragic especially when the solutions are simple -- things like vaccinations against measles or using a mosquito net to reduce the chance of getting malaria."

Becks mingles with locals in Sierra Leone.

Perhaps in a bid to ensure his message received the widest possible audience, Posh Spice's easy-on-the-eyes spouse was photographed sans shirt as he kicked around a soccer ball with some local youths.

"The people playing couldn't believe David Beckham had joined in their game. He was completely natural with them," a UNICEF rep tells the London Sun. "They mobbed him and David took off his T-shirt and gave it to one of the players as a memento."

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