John C. Reilly
Dewey Cox

Jenna Fischer
Darlene Madison

Raymond J. Barry
Pa Cox

Kristen Wiig
Edith

Tim Meadows
Sam

Harold Ramis
L'Chaim

Margo Martindale
Ma Cox

Chris Parnell
Theo

Matt Besser
Dave

Nat Faxon
Awards Show Stage Manager

Conner Rayburn
Dewey Age 8

Gerry Black
Harmonica Player

Jack Donovan Saperstein
Teenage Band

E.J. Callahan
Second Man at Talent Show

Rance Howard
Preacher

Craig Robinson
Bobby Shad

Paul Bates
Nightclub Manager

Patrick Faucette
Bad Men Bass Player

Phil Rosenthal
Mazeltov

Martin Starr
Schmendrick

Jack McBrayer
DJ

Molly C. Quinn
Teen with Pinups

John Ennis
The Big Bopper

Frankie Muniz
Buddy Holly

Ed Helms
Stage Manager

Jack White
Elvis Presley

Angela Little
Beth Anne

Odette Annable
Reefer Girl

Tyler Nilson
Bert

Ian Roberts
Drug Dealer

Steve Bannos
Prison Guard

Willow Geer
Rehab Nurse

David Doty
Rehab Doctor

Jack Kehler
Press Conference Reporter

Gerry Bednob
The Maharishi

David Krumholtz
Schwartzberg

Tim Bagley
Engineer

Jane Lynch
Gail the Television Reporter

Skyler Gisondo
Dewdrop

Simon Helberg
Dreidel L'Chaim

Jackson Browne
Jackson Browne

Jewel
Jewel

Lyle Lovett
Lyle Lovett

Stacey Scowley
Pierced Eyebrow Girl

Ghostface Killah
Ghostface Killah

Otis Williams
The Temptations

Eddie Vedder
Eddie Vedder

Jack Black
Paul McCartney (uncredited)

Paul Rudd
John Lennon (uncredited)

Justin Long
George Harrison (uncredited)

Jason Schwartzman
Ringo Starr (uncredited)

Patrick J. Adams
The Kid (uncredited)

Clement Blake
Edith's Father (uncredited)

Patrick Duffy
Patrick Duffy (uncredited)

Morgan Fairchild
Morgan Fairchild (uncredited)

Paul Feig
Different DJ (uncredited)

Amber Hay
LSD Vision (uncredited)

John Michael Higgins
Record Producer (uncredited)

Jonah Hill
Older Nate (uncredited)

Cheryl Ladd
Cheryl Ladd (uncredited)

Cheryl Tiegs
Cheryl Tiegs (uncredited)

Serria Tawan
70's African American Woman (uncredited)

Adam Herschman
Jerry Garcia (uncredited)