Jimmy Fallon premieres as the new host of The Tonight Show, welcoming his first guest Will Smith and a performance from U2.

Jimmy Fallon has fellow NBC alums Jerry Seinfeld and Kristen Wiig, as well as a performance from Lady Gaga.

Jimmy Fallon has American Hustle's Bradley Cooper and a performance from Tim McGraw on Wednesday's Tonight Show.

First Lady Michelle Obama and Will Ferrell stop by The Tonight Show, as well as a performance by Arcade Fire.

Jimmy Fallon teams up with guest Justin Timberlake for Friday's Tonight Show.

Jimmy welcomes Reese Witherspoon, Fred Armisen and Rick Ross with The Roots.

Jimmy welcomes Paul Rudd, Shaquille O'Neal and Hannibal Buress to The Tonight Show.

Jimmy welcomes Drew Barrymore, Adam Sandler and Dierks Bentley to The Tonight Show.

Tina Fey. Also: Randy Newman performs and is interviewed.

Jimmy has Liam Neeson, Lindsay Lohan, and a musical performance by Bad Things

Billy Joel performs and is interviewed. Also: Chelsea Clinton.

Kevin Bacon; Jeff Musial. Also: Ty Dolla Sign performs; Ann Wilson sits in with The Roots.

Arnold Schwarzenegger (Sabotage (2014); Carson Daly. Also: Vampire Weekend perform.

Colin Firth (Les voies du destin (2013); Chloë Grace Moretz. Also: Nas performs with Q-Tip; John Oates sits in with The Roots.

Anne Hathaway (Rio 2 (2014)); Marlon Wayans (A Haunted House 2 (2014)). Also: Cat Stevens (aka Yusuf Islam) performs.

Jennifer Garner (Draft Day (2014)); Dave Grohl and Krist Novoselic; Stevie Nicks performs with The Roots.

Kevin Costner (Draft Day (2014)); Danica McKellar. Also: Alan Cumming and the cast of Broadway's "Cabaret" perform; Philip Bailey sits in with The Roots.

Nicolas Cage; Emily VanCamp. Also: KISS perform.

Brian Williams (NBC Nightly News with Lester Holt (1970)); Christina Hendricks (Mad Men (2007)); chef Ilan Hall.

David Duchovny; John Oliver. Also: Rita Ora performs.

Actress Cameron Diaz; comic Jim Gaffigan. Also: Future performs with Pusha T and The Roots.

Dr. Phil McGraw; James Van Der Beek. Also: Courtney Barnett performs; Steven Tyler & Joe Perry sit in with The Roots.

Jamie Foxx; Alan Cumming. Also: Alicia Keys & Kendrick Lamar perform.

Emma Stone; Robinson Cano. Also: Keith Urban performs.

Diane Keaton; Dane DeHaan. Also: David Byrne performs; Daley performs with the Roots.

David Spade; Sophia Bush. Also: The Both perform.

Andrew Garfield; Mary Lynn Rajskub. Also: Chvrches perform.

Bryan Cranston (Breaking Bad (2008)); Brie Larson (Community (2009)); Kevin Delaney.

Seth Rogen; Matt Bomer. Also: Coldplay perform.

Comic Louis C.K.; musicians Neil Young and Jack White; Neil Young performs.

Amanda Seyfried; Chad Smith & Will Ferrell Drum Off. Also: Red Hot Chili Peppers perform.

Dave Chappelle. Also: Body Count perform.

Brian Williams raps "Baby Got Back."

Kiefer Sutherland; Nicole Richie; Crosby, Stills and Nash.

Guests include Halle Berry, Chris Colfer and musical guest Florida Georgia Line.

Guests include Kelly Ripa, Joe Manganiello and musical guest Sylvan Esso performs.

Guests include Dana Carvey, Hailee Steinfeld and musical guest MAGIC!

Guests include Liev Schreiber, Rob Reiner and Gabriel Iglesias.

Guests include Michael Strahan, Diane Kruger and musical guest Phish.

Guests include Cameron Diaz, Josh Gad and musical guest Bleachers.

Guests include Whoopi Goldberg, Stephen Moyer and musical guest Puss n Boots.

John Lithgow (The Homesman (2014)); model Miranda Kerr. Also: Jason Mraz performs.