Sister Simone Campbell discusses her "Nuns on the Bus" tour and explains how Paul Ryan's budget battle fails Jesus and the Constitution.

Emmy winner Mandy Patinkin describes his character on "Homeland" and shares a comprehensive perspective on terrorism.

Aspirational pup owner Malcolm Gladwell discusses his work on behalf of dogs, the narcissism behind dog breeding, and "The Big New Yorker Book of Dogs."

Grammy winner Diana Krall talks about 1920s jazz and her provocative album cover.

Director Peter Jackson describes New Zealand as the ideal directorial environment for "The Hobbit: An Unexpected Journey."

Andy Serkis explains the difference between motion and performance capture and does his "impersonation" of Gollum.

Actor Martin Freeman congratulates Stephen on his Tolkien quiz victory and shares his best Bilbo Baggins moment.

An annoying Tolkien super fan knows more about Sir Ian McKellen's character in "The Hobbit" than he does.

Cosmologist Sean Carroll discusses his book, "The Particle at the End of the Universe: How the Hunt for the Higgs Boson Leads Us to the Edge of a New World."

Frank Oz discusses his famous performances as Yoda, Fozzie Bear, and more, and explains why he prefers "Little Shop of Horrors: The Director's Cut" over the original.

The legendary singer-songwriter discusses her Tennessee hometown of Sevierville and her nonprofit literacy foundation, Imagination Library.

Senior White House correspondent Jake Tapper explores the fiscal cliff, the war in Afghanistan, and the Taliban's assault on Combat Outpost Keating.

Paleoanthropologist Chris Stringer shares his book, "Lone Survivors: How We Came to Be the Only Humans on Earth."

Pulitzer Prize winner Tony Kushner describes how "Lincoln" is a bit like a state basketball tournament movie.

The former presidential candidate explores historical fiction, George Washington's leadership and America's future moon base.

The famous filmmaker talks about the Dust Bowl's devastation and the 1989 Central Park jogger case involving five innocent teens.

The MSNBC host talks about conservative election coverage and shares her book, "Drift: The Unmooring of American Military Power."

Pulitzer Prize winner Doris Kearns Goodwin tells one of Abraham Lincoln's dirty stories and quotes some of history's presidential losers.

Editor Andrew Sullivan believes that Europe will follow Barack Obama's national employment strategies and hopes for a civil war within the Republican Party.

New York Times blogger Nate Silver shares his book, "The Signal and the Noise: Why So Many Predictions Fail -- but Some Don't."

New York rockers David Byrne and St. Vincent discuss Hurricane Sandy, brass ensembles and their collaborative album, "Love This Giant."

Lilly Ledbetter discusses her book, "Grace and Grit: My Fight for Equal Pay and Fairness at Goodyear and Beyond."

Indiana Governor Mitch Daniels shares his book, "Keeping the Republic: Saving America by Trusting Americans," and endorses Stephen's book, "America Again."

Historian Anthony Everitt talks about Rome's initial lack of culture, brutal empire conquests and his favorite ruler, Julius Caesar.

John Grisham talks about his rivalry with Stephen King, his days as a starving lawyer, and his latest book, "The Racketeer."

MIT Professor Donald Sadoway plans to minimize the world's oil dependence with the first liquid metal battery.

The alternative rock band chats about Mitt Romney's iPod and clears up a confusing song line for Stephen.

Tyler Perry talks about African-American actors in Hollywood, the upcoming election and his latest film, "Alex Cross."

Newark Mayor Cory Booker reviews Barack Obama's debate performance, Democratic support for faith-based programs and his online activism project, #waywire.

Journalist Evan Thomas describes President Eisenhower's moderate Republicanism, bluffs with nuclear weapons and relationship with the CIA.

In her book "Plutocrats," Chrystia Freeland argues that today's global economy allows the super rich to disregard the American middle class.

Naomi Wolf explores low sexual desire among women, vaginal anatomy and America's outdated cultural script on sex.

The former lead singer of "The Smiths" talks about the Queen's Diamond Jubilee, radical vegetarianism and his song "Meat Is Murder."

Former astronaut Mark Kelly recalls the Endeavour's final mission, Stephen's shuttle landing and the story behind "Mousetronaut."

Molecular geneticist George Church shares his book, "Regenesis: How Synthetic Biology Will Reinvent Nature and Ourselves."

Country music legend Kenny Rogers discusses his jazz beginnings and trusts that his song "The Gambler" is a metaphor for something.

Mexican journalist Jorge Ramos discusses the presidential election, self-deportation and the civic contributions of undocumented immigrants.

Alternative rock trio Ben Folds Five says that their band name was supposed to be comical, but even their manager didn't think it wasn't funny.

"Breaking Bad" executive producer Vince Gilligan talks about meth street names and human nature.

Philosopher Jim Holt tries to solve the mystery of the universe without involving God or scientific laws.

American boxer Claressa Shields talks about the London Olympics, weight classes and Stephen's punchable head.

Award-winning documentarian Errol Morris discusses the Jeffrey MacDonald murder case, the modern court system and his interview machine, the Interrotron.

Acclaimed violinist Itzhak Perlman shares his early fascination with classical music and questions the Colbert Bump.

CNN's senior legal analyst Jeffrey Toobin discusses the Obamacare Supreme Court decision, Super PACs and Ruth Bader Ginsburg.

Harvard University President Drew Faust describes the sociopolitical impacts of the Civil War, including the triumph of the human spirit.

Governor Ed Rendell talks about his book, "A Nation of Wusses: How America's Leaders Lost the Guts to Make Us Great."

Former U.S. Ambassador Bill Richardson shares how Barack Obama can appeal to Hispanic voters beyond immigration issues.

Award-winning journalist Michael Grunwald defends the Obama administration's 2009 Recovery Act, but says only six percent of Americans believe it worked.

CNN contributor Reihan Salam examines Paul Ryan's GOP convention speech and suggests that Republicans did their best to work with President Obama.

Political consultant James Carville discusses the middle class, the Democratic National Convention and Barack Obama's chances of reelection.

Governor Jon Huntsman skips the Republican National Convention to talk about campaign finance, Republican policies and the presidential election.

Stanford University Professor Jennifer Burns discusses Ayn Rand's influence on right-wing politics, her creation of objectivism, and her denunciation of Ronald Reagan.

Newsweek columnist Andrew Sullivan calls for increased bipartisanship and defends his support for Barack Obama in terms of civil rights and tackling national debt.

The Flaming Lips' lead singer, Wayne Coyne, discusses his 13-year stint at Long John Silver's, stolen music equipment and his "fwends" Kesha and Yoko Ono.

Former music executive Santigold sheds light on her herky-jerky choreography and says she would have signed herself back in the '90s.

Indie rock group Grizzly Bear compare their music to a disorienting lifeboat and sings a round with Stephen.

The band fun. talks about undergarments, Super Bowl ads and their run-in with a Swedish death metal group.

Actor Woody Harrelson talks about his long-lost friend Frankie Hyman and the inspiration for their Off-Broadway show, "Bullet for Adolf"

Journalist Liza Mundy shares her book, "The Richer Sex: How the New Majority of Female Breadwinners is Transforming Sex, Love and Family."

The VP of Save the Children's U.S. Programs, Mark Shriver, talks about his father's civic contributions, the War on Poverty, and the importance of investing in kids.

Legendary folk artist Pete Seeger talks about his former Communist Party affiliation, his socialist musician father and the rights to his songs.

The host of MSNBC's "Up with Chris Hayes" explains America's housing bubble, elitism and the difference between educational opportunities and outcomes.

NASA physicist John Grunsfeld maps out Curiosity's landing course and considers whether or not there's life on Mars.

American artist Jeff Koons explains his famous sculpture, "Blue Balloon Dog," the museumgoer's experience, and the importance of bringing art to underserved children.

Legendary comedian Joan Rivers explains why she hates the Olympics, babies, young people, old people and herself.

Senior British diplomat Peter Westmacott talks about London's Olympic planning, royal etiquette and England's shared values with America.

The Brady Campaign's President, Dan Gross, talks about the Colorado shooting tragedy, everyday gun violence, and the prospect of Second Amendment regulations.

Award-winning journalist James Fallows examines the growth of China's aircraft business and what it means for U.S. aerospace exports.

Documentary filmmaker Vikram Gandhi discusses his fake spiritual movement, Mirror philosophy and leader Kumare's second coming.

Lisa Jackson details the EPA's founding under Richard Nixon, the importance of healthy communities, and the effects of mercury on children's IQ.

Mayor Annise Parker highlights Houston's largest industries and talks about being the first openly gay mayor of a major American city.

Nas shares his passion for rapping, thoughts on retirement, and the inspiration behind his 10th album cover.

Princeton University professor Anne-Marie Slaughter stresses that women need better job choices, ones that equally accommodate a family and full career.

Academy Award-winning screenwriter Aaron Sorkin talks about the golden age of news, "The West Wing" and what makes America the greatest country.

Philanthropist Melinda Gates discusses foreign aid, her philosophy on contraception, and the Bill & Melinda Gates Foundation's global family planning summit.

Award-winning American novelist Richard Ford shares his inspiration for "Canada," aversion to criticism, and logic behind storing manuscripts in the freezer.

Frank Deford talks about his long sports writing career, his face-off with the Harlem Globetrotters, and the establishment of Title IX.

Cosmologist Lawrence Krauss discusses his book "A Universe from Nothing: Why There Is Something Rather than Nothing."

Newsweek correspondent Daniel Klaidman discusses his book "Kill or Capture: The War on Terror and the Soul of the Obama Presidency."

Actress Olivia Wilde talks about campaigning for Barack Obama, competing in dressage, and joining Stephen on Maxim's Hot 100 list.

Nobel Prize winner Paul Krugman discusses America's recessions and depressions, the effect of affluence on politics, and Europe's big economic mistake.

Pulitzer Prize-winning journalist Steve Coll talks about ExxonMobil's corporate model, management and international reputation.

Gregg Allman of the Allman Brothers Band talks about fame, military school and the band's first flight on his Boeing 720, in his memoir, "My Cross to Bear."

MacArthur Genius Fellow Will Allen discusses urban farming and his book, "The Good Food Revolution: Growing Healthy Food, People, and Communities."

Actor Martin Sheen discusses "The Amazing Spider-Man," lefty-liberalism and his given Latino name.

Singer-songwriter Regina Spektor explains her appreciation for her childhood immigration experience and her love of Russian culture.

Actor Neil Patrick Harris discusses hosting the Tony Awards, performing on Broadway and playing a convincing straight guy on "How I Met Your Mother."

Second Lady Jill Biden describes her passion for teaching, the resilience of military families, and her "Vice team" leadership.

Congressman John Lewis recalls the 1965 Selma-to-Montgomery March, America's segregation and his mentor Martin Luther King, Jr.

Author Jack Hitt explores America's self-made history, job creators and the cyclical nature of amateurism.

Actor Alan Alda discusses good business models, the World Science Festival and his international Flame Challenge.

Actress Charlize Theron discusses fairy tales, beauty, and Stephen's prizewinning switch from handsome man to hot woman.

Dr. Francis Collins talks about America's weight problem, evolution and the holistic way to confront obesity.

Vogue editor-in-chief Anna Wintour discusses The Met's Costume Institute exhibit "Schiaparelli and Prada: Impossible Conversations."

Civil rights lawyer Michelle Alexander discusses her book "The New Jim Crow: Mass Incarceration in the Age of Colorblindness."

Bravo executive and talk show host Andy Cohen discusses his book "Most Talkative: Stories from the Front Lines of Pop Culture."

Lena Dunham discusses "Girls," her popular HBO show about young women navigating work, love and friendship in New York City.

Social psychologist Jonathan Haidt discusses his book "The Righteous Mind: Why Good People Are Divided by Politics and Religion."

Carne Ross discusses his book "The Leaderless Revolution: How Ordinary People Will Take Power and Change Politics in the 21st Century."

Academy Award-winning actress Diane Keaton skirts Stephen's questions and misinterprets a backstage hug.

Jack White introduces his first solo album, "Blunderbuss," and recalls making a record with Stephen.

Harvard University's Michael Sandel illustrates the ethical and moral concerns regarding the growing role of money and market values in society.

The world's third youngest Chess Grand Master Magnus Carlsen discusses game strategy and stardom.

Former Texas Board of Education Chairman Don McLeroy discusses the documentary "The Revisionaries," science in textbooks and religious conservatism.

Tavis Smiley and Cornel West talk about their book on American poverty, "The Rich and the Rest of Us."

Arianna Huffington discusses the Huffington Post's Pulitzer Prize and how it differs from Stephen's Peabody Award.

Jonah Lehrer examines dangerous creativity myths and the history of innovation.

Award-winning American singer Bonnie Raitt talks about environmental activism and her popular track "Angel from Montgomery."

James Cameron discusses the "Titanic 3D" release and the submarine he helped engineer to dive straight to the bottom of the Marianas Trench.

Michelle Obama discusses her national initiative for helping military families, Joining Forces, and the importance of lowering veterans' unemployment rates.

Higher education consultant Richard Hersh believes in challenging college students to develop their highest intellectual and emotional capabilities.

Auto executive Bob Lutz discusses the soul of the American car industry, Mitt Romney and the award-winning Chevy Volt.

Novelist Anne Rice discusses her book "The Wolf Gift," and whether or not she fears an eternity of being poked in the hiney with a hot pitchfork.

National Geographic explorer-in-residence Robert Ballard talks about "Save the Titanic," his documentary promoting its preservation and protection against tourism.

Governor Nikki Haley talks about the good people of South Carolina who elected a 38-year-old, Indian-American female for governor.

Libertarian presidential candidate Governor Gary Johnson believes in fiscal conservatism and social tolerance.

Peter Beinart discusses his book "The Crisis of Zionism" and what he sees as a divide between the democratic Israel and the Israel of the West Bank.

Actor Mark Ruffalo became an anti-fracking, clean water activist after seeing the technologies' detrimental impact on communities in Pennsylvania.

Charles Murray talks about his book, "Coming Apart: The State of White America, 1960 to 2010," and suggests a way to address the growing division between the classes.

Dr. David Page, director of the Whitehead Institute for Biomedical Research, defends the Y chromosome in the face of enumerable challenges and insults to its character.

Combat journalist Dexter Filkins discusses the disconnect between preconceived notions about other countries and the realities on the ground.

Veteran political strategist Mark McKinnon's No Labels movement has a 12-step program to reform Congress.

Andrew Bird explains the inspiration for "Eyeoneye" and learns of sad associations with his "The Mysterious Production of Eggs" album.

Journalist Katherine Boo talks about what her experience in Mumbai, India, has taught her about poverty in the United States.

Stephen prank calls Eric Bolling, is inspired by Herman Cain's avant-garde ad, and talks folk music with Elvis Costello, Emmylou Harris and Don Fleming.

Willem Dafoe explains his transformation into a nine-foot Martian for the movie "John Carter."

Jonathan Safran Foer discusses his book "The New American Haggadah" and explains the Jewish Passover tradition of retelling stories.

Audra McDonald gives some historical background on "Porgy and Bess" and explains why it's not a musical about Stephen.

Claire Danes talks about her role as a bipolar CIA agent in her TV show "Homeland."

William Shatner discusses love, life, horses and his Broadway show "Shatner's World."

Ross Eisenbrey believes that everyone -- from interns to college athletes --should be paid for working for someone else's financial benefit.

Peggielene Bartels describes the Ghanaian libation ritual and discusses her achievements as the king of Otuam.

Spanish tenor Placido Domingo talks about his world-famous production of "Tosca" and explains why women find tenors so captivating.

House Democratic Leader Nancy Pelosi believes that super PACs threaten American democracy and that Citizens United should be overturned.

Author Robert Kagan talks about advising Mitt Romney on foreign policy and explores America's use of military force in international affairs.

Novelist Ann Patchett discusses the importance of brick-and-mortar bookstores and explains what prompted her to open Parnassus Books in Nashville.

The New York Times' William Broad explores the sexual benefits of yoga as well as its potential health risks.

Activist Bill McKibben talks about the proposed Keystone XL oil pipeline and calls on Colbert Nation to sign his petition opposing its construction.

CNN's Christiane Amanpour examines the likelihood of America and Israel going to war with Iran and weighs in on Iran's nuclear program.

CeaseFire's Ameena Matthews explores how her tough inner-city upbringing informs her work as a peacemaker among Chicago's gangs.

Bjork shows off her "Biophilia" album iPad app and explains what inspired her interactive multimedia collection.

Harvard Law School professor Laurence Tribe discusses the function of the Constitution and reveals his favorite amendment.

Drew Barrymore recalls working with Steven Spielberg as a little girl and thinks about recording a whale CD to promote her movie "Big Miracle."

NPR host Terry Gross talks about her 25-year career in public radio and offers the inside scoop on her interviews with Grover Norquist and Bill O'Reilly.

The Daily Beast's Andrew Sullivan analyzes the picture that GOP candidates have painted of Barack Obama and extolls the president's numerous achievements.

Bruce Bueno de Mesquita explains how he uses game theory to make geo-political predictions and formulate car-buying strategies.

The Metropolitan Museum of Art's Carrie Rebora Barratt provides an analysis of Emanuel Leutze's masterpiece "Washington Crossing the Delaware."

Columnist David Frum calls for an economically inclusive, environmentally responsible and socially modern Republican party.

Jennifer Granholm explains the fundamental differences between the Obama administration's intervention in the auto industry and Mitt Romney's work at Bain Capital.

Activist Scott Douglas advocates the overturn of Alabama's HB 56 anti-immigrant law and calls for a single, fair immigration law across the U.S.

Politico's Mike Allen analyzes Stephen's prospects in South Carolina, should he choose to make an even more historic announcement.

George Stephanopoulos considers the likelihood of Mitt Romney winning the GOP nomination and of Hillary Clinton becoming Barack Obama's vice presidential running mate.

Bill Moyers believes that capitalism is out of control and there can be no people's democracy as long as corporations are considered people.

Author Melissa Harris-Perry deconstructs stereotypes of African-American women and considers the consequences of a white-male-centered perspective on the American story.

AOL co-founder Steve Case believes that a generational shift away from ownership and toward community sharing is taking place.

Journalist John Heilemann examines Rick Santorum's rise in the Iowa caucus and the potential direction of his campaign.

Senator Bernie Sanders calls on Americans to support his proposed Saving American Democracy Amendment and help overturn the Supreme Court's Citizens United decision.