Ben Stiller discusses the power of imagination, celebrating the holidays and his movie, "The Secret Life of Walter Mitty."

"47 Ronin" star Keanu Reeves learns about the three things that make Stephen angry and offers his own contributions to the "Sad Keanu" meme.

Garry Trudeau talks about the inspiration for his political comedy series "Alpha House" and helpfully explains the concept of streaming video for Stephen.

BuzzFeed's Jonah Peretti talks about his company's embrace of journalism and reflects on the future of media.

"The Unwinding" author George Packer discusses income inequality and institutional failure in America.

Elizabeth Gilbert talks about "The Signature of All Things," her sweeping novel about a woman botanist in the 19th century.

NPR's Alex Blumberg talks about the experience of following a T-shirt throughout the production process, from Mississippi to Indonesia to Bangladesh.

"A Case For Climate Engineering" author David Keith explains his proposal to use geoengineering as a means of slowing climate change.

Ford CEO Alan Mulally talks about the 50th anniversary of the Mustang, the 2008 auto bailout and revitalizing Detroit's economy.

The Equal Justice Initiative's Bryan Stevenson makes the case for reforming America's criminal justice system.

NASA pioneer Ed Stone discusses the significance of the ongoing Voyager 1 mission, from its launch in 1977 to its arrival in interstellar space.

"Focus" author Daniel Goleman describes the concept of emotional intelligence and the relationship between mental focus and success.

Director and author J.J. Abrams talks about his passionate fan base, directing "Star Trek," and the origin of his interactive novel, "S."

Rapper M.I.A. talks about her Sri Lankan roots, blending politics with music, and the American songwriters who inspire her.

Rick Santorum shares his thoughts on the 2016 presidential election, the meaning of marriage and his movie, "The Christmas Candle."

"12 Years a Slave" director Steve McQueen talks about his film's historical roots, the brutality of slavery, and his view of Solomon Northup as an American hero.

"Without Their Permission" author Alexis Ohanian discusses Reddit, crowdfunding and the value of a free and open Internet.

Blind Boys of Alabama founding member Jimmy Carter talks about performing since 1944, his love for gospel music and the secret to his youthful appearance.

"Big History" host David Christian talks about the importance of understanding history on a large scale, from the origin of the universe to modern times.

"Days of Fire" author Peter Baker talks about the complex and contentious relationship between Dick Cheney and George W. Bush.

"The Story of the Human Body" author Daniel Lieberman talks about the many ways humans have evolved over the past 10,000 years.

The host of WNYC's "The Brian Lehrer Show" discusses Bill de Blasio's election, Michael Bloomberg's legacy and Chris Christie's rare political gift.

Julius Erving discusses a canceled basketball game that would have given Stephen the greatest show of his life.

"Murdoch's World" author David Folkenflik talks about Rupert Murdoch's media empire, his influence on world leaders and the extent of the News Corp phone-hacking scandal.

Zach Sims discusses Codecademy, his wildly popular website that provides free coding lessons to over 10 million people.

16-year-old Jack Andraka explains how he devised a new way to detect cancer, which earned him the grand prize at the Intel International Science and Engineering Fair.

Billy Collins talks about his writing persona and the responsibilities of a poet laureate before joining Stephen in a joint reading from "Aimless Love."

Orlando Bloom talks about his Broadway debut in "Romeo and Juliet," his love of the theater and his preference for iambic pentameter.

The multi-talented Stephen Fry talks about atheism, activism and his Broadway debut in Shakespeare's "Twelfth Night."

Judy Woodruff and Gwen Ifill discuss anchoring the PBS NewsHour, the importance of in-depth reporting and the extent to which they are beholden to Big Donator.

"Wilson" author A. Scott Berg explains why he believes Woodrow Wilson is the most influential figure of the 20th century.

Will and Win Butler talk about their favorite Canadian bands, the pretentiousness of Arcade Fire and how their experience in Haiti inspired them to form The Reflektors.

Reed Albergotti and Vanessa O'Connell discuss their book, "Wheelmen: Lance Armstrong, the Tour de France, and the Greatest Sports Conspiracy Ever."

Tom Hanks discusses his film "Captain Phillips," which portrays the 2009 capture of Richard Phillips by Somali pirates.

"Parkland" star Paul Giamatti talks about being an approachable celebrity and playing Abraham Zapruder, the man who accidentally filmed John F. Kennedy's assassination.

Skipper James Spithill discusses yacht racing technology, the America's Cup and Larry Ellison's ocean of cash.

The Washington Post's David Finkel shares his book about the mental wounds of veterans, "Thank You for Your Service."

"Tip and the Gipper" author Chris Matthews discusses the government shutdown, Ronald Reagan's leadership style and the Geneva Summit.

"Harry Potter" star Daniel Radcliffe talks about playing beat poet Allen Ginsberg in the biographical film "Kill Your Darlings."

"Breaking Bad" creator Vince Gilligan discusses the fate of his main character, Walter White.

OCEARCH founder Chris Fischer discusses the detrimental effects of shark finning in Asia.

"Don Jon" director Joseph Gordon-Levitt examines what porn and romantic comedies have in common.

Lars Ulrich, James Hetfield, Robert Trujillo and Kirk Hammett talk about being angry in your 50s and performing on television.

Singer-songwriter Jack Johnson talks about rock 'n' roll, the "Hawaiian Grammys" and love songs.

Author Nicholson Baker discusses his garden metaphor for life and his desire to rename genitalia.

U.S. Secretary of Education Arne Duncan discusses Obama's Race to the Top initiative and Preschool for All program.

Vietnam veteran Andrew Bacevich discusses his book, "Breach of Trust: How Americans Failed Their Soldiers and Their Country."

Former FBI Senior Intelligence Advisor Philip Mudd talks about Al Qaeda, Syria, Colin Powell's WMD speech and enhanced interrogation techniques.

Grammy winner Sheryl Crow talks about country music and anti-war activism.

"Salinger" author and director Shane Salerno talks about J.D. Salinger's lost love Oona O'Neill and the reason for Seymour Glass' suicide in "A Perfect Day for Bananafish."

Tennis legend Billie Jean King talks about her 1973 "Battle of the Sexes" match against Bobby Riggs.

Folk legend John Prine recalls his time working as a mailman and explains why he's opposed to twerking.

Meteorologist Gary England locates Tornado Alley on a map and defends residents of Oklahoma.

Timothy Cardinal Dolan discusses his e-book, "Praying in Rome: Reflections on the Conclave and Electing Pope Francis."

Duke University President Richard Brodhead talks about his report on the humanities, "The Heart of the Matter."

"House of Cards" actor Kevin Spacey explains why he should get an award for TV even though his show is on the Internet.

Civil rights pioneer John Lewis remembers the March on Washington and the 1965 Selma march.

Senator Sheldon Whitehouse shares his book, "On Virtues: Quotations and Insights to Live a Full, Honorable, and Truly American Life."

"TransAtlantic" author Colum McCann talks about the great Irish novel, St. Patrick's Day and his cross-country bike ride.

"Jobs" star Ashton Kutcher talks about Steve Jobs' innovative mind, brutal honesty and personal history.

Daft Punk abandons StePhest Colbchella '013, Stephen angers his Hyundai sponsors, and Blurred Lines singer Robin Thicke saves Stephen's career.

Actor Hugh Laurie talks about the blues, his drama series "House" and the greatest bond between England and America.

Bryan Cranston recalls his beginnings on "Power Rangers," which likely led to his criminal persona on "Breaking Bad."

Journalist Emily Matchar explains America's re-embracing of lost domestic arts and practices.

Atul Gawande discusses his New Yorker article, "Slow Ideas: Some ideas spread fast. How do you speed the ones that don't?"

The Lumineers talk about moving to Denver and screaming "Ho Hey" at loud audience members.

Former Senator Olympia Snowe talks about her book, "Fighting for Common Ground: How We Can Fix the Stalemate in Congress."

The President of edX, Anant Agarwal, explains the reason for offering free university courses online.

MoMA's Poet Laureate, Kenneth Goldsmith, discusses his book "Seven American Deaths and Disasters."

Kjerstin Gruys shares her book, "Mirror, Mirror Off the Wall: How I Learned to Love My Body by Not Looking at It for a Year."

Academy Award-winning actor Jeff Bridges theorizes about the afterlife and discusses his organization for children, the End Hunger Network.

Comedian Jerry Seinfeld puts no effort into his web series, "Comedians in Cars Getting Coffee."

Tumblr creator David Karp discusses dropping out of high school, selling his site to Yahoo and letting pornographic images slide.

Author Jeremy Scahill discusses the secret war in Afghanistan, drone strikes in Pakistan and Yemen and the Obama administration's "Terror Tuesday" meetings.

New York Senator Chuck Schumer addresses immigration reform, gang violence on the Senate floor, border security and the keys to bipartisan support.

Bill Moyers discusses the decline of the middle class portrayed in his "Two American Families" documentary and recalls the history behind the Voting Rights Act of 1965.

Tufts Professor Peniel Joseph details Section 4 of the 1965 Voting Rights Act, explains colorblind racism and gives a mini history lesson about the civil rights movement.

In his book "Far from the Tree," Andrew Solomon explores how parents respond to children who are dramatically different from them.

"Much Ado About Nothing" director Joss Whedon talks about his name, his modern Shakespeare adaptation and "The Avengers 2."

Jimmy Tamborello, Ben Gibbard and Jenny Lewis celebrate the 10th anniversary of their album, "Give Up."

Paul McCartney discusses the reissue of "Wings Over America," recalls recording "Band on the Run" in Nigeria and debates the pronunciation of "schedule."

"What Do Women Want?" author Daniel Bergner explains that women may be just as promiscuous as men.

Dan Savage shares his book, "American Savage: Insights, Slights, and Fights on Faith, Sex, Love, and Politics."

John Mellencamp, Stephen King and T Bone Burnett reveal the inspiration behind their Southern gothic, supernatural musical.

Jonathan Alter explains how Barack Obama's young geek volunteers crushed Mitt Romney's "Mad Men" campaign during the 2012 election.

Academy Award-winning director Alex Gibney discusses Bradley Manning's WikiLeaks trial and the Obama administration's crackdown on whistleblowers.

The longest-serving congressman in American history explains how Washington has changed over the last 80 years.

The New York Times's C.J. Chivers explains the ways in which the Syrians and Iraqis are involved in the same civil war.

Matt Berninger of The National talks about Cincinnati's staple spaghetti dish, perfectionism and his band's meaningless moniker.

Dr. Noah Feldman defines "Cool War" and explains why America should be afraid of China as a fast-rising, interdependent global superpower.

Environmental journalist David Sassoon discusses dilbit spills, climate change and his online publication, InsideClimate News.

Harvard University's Daniel Lieberman explains that human beings are among the best long-distance runners in the world because they're good at sweating.

Megastar Cyndi Lauper shares the story of a shoe factory owner and drag queen from Broadway's hit musical "Kinky Boots."

Dan Brown discusses Dante's "Inferno," explains why he puts everything in puzzle form and becomes the subject of an anagram.

The couple discuss their book, "Impossible Odds: The Kidnapping of Jessica Buchanan and Her Dramatic Rescue by SEAL Team Six."

Pulitzer Prize-winning author Jennifer Egan helps Stephen smartificate on "The Great Gatsby". Director Baz Luhrmann explains the challenges in adapting F. Scott Fitzgerald's famous novel, and recounts meeting the author's granddaughter.

Richard Besser talks about his book, "Tell Me the Truth, Doctor: Easy-to-Understand Answers to Your Most Confusing and Critical Health Questions."

"Present Shock" author Douglas Rushkoff talks about the dot-com boom, Facebook "friends" and stock derivatives.

The Pulitzer Prize-winning author lists Lyndon Johnson's undertakings, from civil rights and voting rights bills to Medicare and education.

The "Iron Man 3" star talks about playing Gandhi, trembling at his knighting ceremony and portraying a villain.

The independent artists give advice to major music labels and talk about hip-hop's homophobic and misogynistic past.

The founders of Snapchat discuss how their smart phone app promotes more natural and expressive human communication when two people are apart.

An almost-shirtless Iggy Pop recalls driving into a Christmas tree orchard after falling asleep at the wheel.

Bishop Gene Robinson discusses how the church got it wrong about gay, lesbian, bisexual and transgender people.

NASCAR driver Danica Patrick explains how racing is a cardio workout.

Google's executive chairman discusses his book, "The New Digital Age: Reshaping the Future of People, Nations and Business."

"Cooked" author Michael Pollan explains that the most important thing about one's diet is not a nutrient -- it's an activity.

NBC's chief foreign correspondent talks about visiting South Korea, traveling back in time in North Korea, and being taken hostage in Syria.

Alan Cumming discusses Broadway's production of "Macbeth," set in a psychiatric unit.

"Poems to Learn by Heart" author Caroline Kennedy encourages people to steal her book with their minds.

Obama's former Regulatory Affairs Administrator describes government health and safety nudges, like the USDA's "MyPlate."

VICE co-founder Shane Smith discusses his journalism adventures in Taliban-controlled areas, North Korea and labor camps.

Detroit native Charlie LeDuff discusses white flight, black flight, business flight and "dead flight" in his hometown.

President Bill Clinton explains why he doesn't call the Clinton Global Initiative the Clinton American Initiative.

BRAIN Initiative project director Francis Collins discusses the most complicated biological structure in the universe.

The philosopher shares his book, "The God Argument: The Case Against Religion and for Humanism."

The former governor of New Jersey discusses political sex scandals, a program for incarcerated addicts, and his HBO documentary, "Fall to Grace."

The Golden Globe winner discusses her Broadway debut, science fiction roles and television miniseries "Political Animals."

The pediatric endocrinologist shares his book, "Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease."

The owner of Rustik Rooster Farms explains how breeding a Chinese pig and a Russian pig makes a prize-winning German pig.

The cardiologist talks about his book, "The Creative Destruction of Medicine: How the Digital Revolution Will Create Better Health Care."

The MacArthur Fellow discusses path to citizenship, education for undocumented immigrants and the "Superman Question."

The president of NYU believes that baseball, like Catholicism or Buddhism, can be a road to God and that the real meaning of life can't be put into cognitive terms.

The contemporary artist explains why he paints Jif jars and classic American blondes shopping in Wal-Mart.

"Oz The Great and Powerful" star James Franco chats about the "Wizard of Oz" prequel, wicked witches and "The Lord of the Rings."

Witness to Innocence's advocacy director, Kirk Bloodsworth, discusses DNA evidence testing for death row inmates and his quest to abolish the death penalty.

President Obama's former speechwriter talks about his collaborative writing process and the importance of storytelling versus sound bites.

MoMA's Architecture and Design senior curator talks about interfaces, a vase made by bees, and an earthquake-proof school desk.

"Physics of the Future" author Michio Kaku talks about the Apophis asteroid, set to skim by Earth in 2029 and possibly hit in 2036.

Simon Garfield talks about Christopher Columbus' map fiasco and the biggest badass in the history of mapmaking, Claudius Ptolemy.

Lil Buck describes a Memphis street dance called jookin and teaches Stephen the beginner bug jump.

The Game Show Network CEO shares his book, "Catastrophic Care: How American Health Care Killed My Father -- and How We Can Fix It."

The senior editor of Slate discusses her book, "Sticks & Stones: Defeating the Culture of Bullying and Rediscovering the Power of Character and Empathy."

The Lieutenant Governor of California shares his book, "Citizenville: How to Take the Town Square Digital and Reinvent Government."

Dave Grohl talks about Nirvana, L.A.'s legendary Sound City Studios and his touring super group, the Sound City Players.

Roger Hodge talks about his quarterly, The Oxford American, slow-smoked pig and the music of Louisiana.

Gary Willis, the Pulitzer Prize-winning author, talks about transubstantiation, Catholic priesthood and all the trouble that comes from the book of Hebrews.

The Oscar-nominated director discusses his film collective, Court 13, and Louisiana communities that sit on the wrong side of the levee.

The Pulitzer Prize-winning author discusses his book, "Going Clear: Scientology, Hollywood, and the Prison of Belief."

Julie Andrews discusses her Dame Commander rank, latest children's book and celebrated role as Mary Poppins.

Justice Sotomayor discusses her funny colleagues, self-reliant childhood and most conservative belief as an Independent.

Music critic Matthew Guerrieri examines Symphony No. 5, German Romanticism and Beethoven's dating life.

Microsoft's founder talks about polio eradication, information technology and the decline in childhood deaths worldwide.

The MacArthur Grant Fellow uses analogies to explain why he prefers short stories over novels.

Co-founder of The Breakthrough Institute Michael Shellenberger explores global energy consumption, nuclear power and lessons from Frankenstein.

Fashionista Tavi Gevinson describes her online magazine, "Rookie, " the world of teenage girls, and effective fashion styles for Stephen.

The award-winning actress talks about Mary Lincoln's tragic life, Hollywood and the audition that swayed Steven Spielberg.

Kathryn Bigelow defends the firsthand accounts which informed "Zero Dark Thirty" and its portrayal of enhanced interrogation tactics.

Ta-Nehisi Coates discusses President Obama's reelection, the Black Panther Party and Michelle Obama's youthful hairdo.

The legal scholar shares his book, "America's Unwritten Constitution: The Precedents and Principles We Live By."

Network news icon Tom Brokaw discredits calls for Obama's impeachment and describes a few of the nine presidents he's covered since JFK.

The Pulitzer Prize-winning author talks about his book, "The World Until Yesterday: What Can We Learn from Traditional Societies?"

Piers Morgan, who comes from a place without the Second Amendment, quietly points out England's low gun murder rates.

The lead singer of Death Cab for Cutie discusses his relatively universal solo album, "Former Lives."

The biological scientist shares his book, "The Universe Within: Discovering the Common History of Rocks, Planets, and People."

Chris Kluwe explains the punter's role and reiterates his support for pro-gay Ravens linebacker Brendon Ayanbadejo.

Wikipedia co-founder Jimmy Wales explains operating costs, censorship in China and the budding Wikivoyager.