Actor and director Ben Affleck testified before the Senate Foreign Relations Committee on Feb. 26, 2014, on issues facing the Democratic Republic of Congo.
Actor and comedian Seth Rogen also testified before Congress on Feb. 26, 2014, promoting Alzheimer's education at a Senate Appropriations subcommittee hearingon the disease.
Actor and director George Clooney testified before the Senate Foreign Relations Committee on March 14, 2012, about violence in Sudan.
Comedian Stephen Colbert testified before Congress on Capitol Hill in September 2010. Colbert spoke about the plight of migrant workers at the Immigration, Citizenship, Refugees, Border Security, and International Law Subcommittee hearing on Protecting America's Harvest, on Sept. 24, 2010.
Actor Kevin Costner speaks on the Department of Homeland Security's response to the Gulf oil spill during a House of Representative's Committee on Homeland Security hearing on Sept. 22, 2010.
U2 lead singer Bono arrives to meet the Senate Foreign Relations Committee on Capitol Hill in Washington, Oct. 3, 2007.
Bono has made several trips to Washington. Here, he testifies at a Senate Appropriations hearing on AIDS programs and research, on Capitol Hill in Washington, May 18, 2004.
Actor Ted Danson testified in July 2010 before the Subcommittee on International Trade, Customs, and Global Competitiveness in July on trade practices and policies of the seafood industry. The photo here was taken outside an Oceana Partner's event in Pacific Palisades, Calif., on Oct. 18, 2008. Oceana is an organization dedicated to protecting and restoring the world's oceans.
Actor James Earl Jones testified in 2002 before the House Education Reform Subcommittee on how corporate sponsorships improved literacy rates in the U.S. The same year, he was honored at the Kenney Center (see photo) for lifetime contributions to American culture.
Actor David Hyde Pierce testified before the Senate Subcommitte on Labor, Health and Human Services in April 2002 about his loved ones affected by Alzheimer's disease. In this photo, Pierce (L) is with Martin Short appears at the premiere for "Treasure Planet." The two men provided voices for the animated film.
Actress Julia Roberts testified in May 2002 before the House Appropriations Subcommittee on RETT syndrome.
Actor Michael J. Fox and boxer Muhammad Ali both testified before the Senate Appropriations Subcommittee on Health and Human Services in May 2002 on Parkinson's disease. In this 2006 photo, the two men attend a benefit for the Michael J. Fox Foundation for Parkinson's research in New York City.
Boston Red Sox pitcher Curt Schilling is sworn in during a congressional investigation in 2005 on steroid use in baseball. The hearing included several current and former players, as well as officials and family members affected by steroid-related suicide, who testified about alleged drug use in baseball.
Actor Christopher Reeve smiles during his news conference on Capitol Hill on May 15, 1996. Reeve appeared before Congress to lobby for increased funding for spinal cord injury research.
Singer Harry Connick Jr. testifies during a hearing on Hurricane Katrina relief before the Senate Finance Committee in October 2005.
Julia Ormond, actress and goodwill ambassador for the abolition of slavery and human trafficking, testified during a House International Relations Committee hearing in June 2006. In this photo from May 2006, Ormond participates in a conference on the same topic in Bangkok.
Academy Award winning actress and Goodwill Ambassador Mira Sorvino attends a news conference with Rep. Christopher Smith (R-NJ) about the crisis in Sudan. Sorvino testied in September 2006 before the House of Representatives International Relations Committee on the situation in Sudan.
Actor and activist Don Cheadle testifies before the Senate Human Rights and The Law Subcommittee in February 2007 on genocide. In this photo from the hearing, Cheadle appears with Canadian Lt. Gen. Romeo Dallaire, former commander of the U.N. peacekeeping forces in Rwanda. Cheadle starred in the movie "Hotel Rwanda."
Actor Chris Klein testified at a hearing before the House Appropriations Subcommittee on the Interior in March 2007 on the importance of investing in the arts. In this photo from January of the same year, Klein poses at the premiere of "The Good Life" at the Sundance Film Festival.
Singer and songwriter Jewel, seen here at the 2007 Young Hollywood Awards, testified before the House Income Security and Family Support Subcommittee on disconnected and disadvantaged youth in June 2007. Jewel was homeless as a teenager in San Diego.
Hall of Fame tight end and head coach Mike Ditka listens during a congressional hearing on the National Football League's system for compensating retired players in September 2007.
Singer Elton John, seen here performing at a charity event in Beverly Hills in October 2002, appeared before a hearing in April of that year to call for more funding to fight AIDS globally.
Actor Richard Gere testified at a hearing before the Senate East Asian and Pacific Affairs Subcommittee in April 2008 on the crisis in Tibet.
Actor and Enterprise Foundation trustee Ed Norton testified at a Capitol Hill hearing on green building standards in May 2008. Norton appears in this photo at a screening of "Leaves of Grass" at the Toronto International Film Festival in September 2009.
Singer Alanis Morissette testifies in April 2001 during a hearing on online entertainment before the Senate Judiciary Committee.
Singer Nick Jonas testified in June 2009 during a Senate hearing on the need for federal funding for Type 1 diabetes research. In this January 2009 photo, Jonas appears at a Disney Channel promotion.
Singer John Legend and actress and actress Kerry Washington testify at the House Appropriations Committee hearing on funding for the arts in April 2008.
Comedian Jerry Lewis, national chairman of the Muscular Dystrophy Association, testified before a Senate health subcommittee in February 2001 during a hearing on muscular dystrophy. In this photo, he appears on "Larry King Live" in 1999.
Actor Dennis Quaid listens to remarks as he testifies at a Capitol Hill hearing on the drug Heparin in May 2008. Quaid is the father of twins who nearly overdosed on Heparin, an injectable anticoagulant, as newborns.
Actress and Goodwill Ambassador Nicole Kidman testifies before the House Foreign Affairs Subcommittee On International Organizations, Human Rights And Oversight in October 2009 on violence against women.