He's won an Oscar and been dubbed the "Sexiest Man Alive" twice, but George Clooney's finest legacy may well be his philanthropic work. Clooney has been a driving force behind MTV's "Hope for Haiti Now" telethon, making it the latest milestone in Clooney's long history of volunteer service.

Clooney's parents, Cincinnati newsman Nick and his wife, Nina, fostered their children's philanthropic spirit early on. "Partly because I was in news and television for all those years and a public person in local markets, we were always doing [charity events], always going to fundraisers once or twice a week, and the kids would go," Nick Clooney told MTV News. "We'd collect cans of food for the free stores or we would try to do the fundraisers for the various school projects or hospitals. That sort of thing went on regularly, but I must say the folks next door did the same thing."

As Clooney's star rose in Hollywood, so did his ability to raise awareness for the social issues he champions. "He understands that [celebrity] is a gift, and if you don't use gifts they simply atrophy, so he does whatever he can to make sure that those around him whose lives he can affect get a fair shake," Nick explained.

One of Clooney's first high-profile projects was 2001's "America: A Tribute to Heroes," a telethon in support of the families of victims of the 9/11 terrorist attacks. The event featured performances by Mariah Carey, Alicia Keys and Paul Simon and raised more than $150 million for the United Way of New York City's September 11th Telethon Fund.

Three years later, in the aftermath of the 2004 Indian Ocean tsunami, Clooney helped organize NBC's "Tsunami Aid: A Concert of Hope," which aired in January 2005. A slew of stars were recruited to answer calls, including Matt Damon, Brad Pitt, Leonardo DiCaprio, Ben Affleck and Johnny Depp. The telethon, which also featured performances by Madonna and Christina Aguilera, raised $18.3 million for the American Red Cross International Response Fund.

An ongoing concern for Clooney has been the war-torn region of Darfur. In 2006, the actor, along with father Nick, traveled to Sudan to film the documentary "A Journey to Darfur," which aired on the AmericanLife channel. In 2008, the film was released on DVD with proceeds going to the International Rescue Committee. Clooney has testified before the U.N. regarding the genocide and was listed in the Time 100 for his humanitarian work in the region. He continues to raise funds for Darfur, in addition to Burma and Zimbabwe, through his charity Not On Our Watch, which he co-founded with producer Jerry Weintraub, human-rights lawyer David Pressman and his "Ocean's Eleven" co-stars Don Cheadle, Matt Damon and Brad Pitt.

For tonight's telethon, which will feature more than 130 actors, athletes, musicians and television hosts, Clooney has one simple goal: to raise a lot of money. "That's it. ... Just first and foremost that we can raise a lot of money," he told MTV News Thursday. "If I thought that we could all pick up shovels and go in there and not be in the way, I think a lot of people would do that."

Ultimately, Clooney's plea for Haiti encapsulates his own lifelong giving philosophy. "It's a big world out there and we all have a lot of responsibility to look out for people who can't look out for themselves," he said.

Learn more about what you can do to help with [article id="1629607"]earthquake-relief efforts in Haiti[/article], and for more information, see Think MTV. Join George Clooney and Wyclef Jean for [article id="1630214"]MTV's "Hope for Haiti Now" telethon[/article], airing commercial-free Friday, January 22, at 8 p.m. ET, and visit HopeForHaitiNow.org or call (877) 99-HAITI to make a donation now.