- Brian Dunkleman - Self - Host
- Keith Urban - Self - Judge
- Paula Abdul - Self - Judge
- Harry Connick Jr. - Self - Judge
- Ellen DeGeneres - Self - Judge
- Ellen DeGeneres - Self
- Mariah Carey - Self - Judge
- Mariah Carey - Self
- Mariah Carey - Self - Mentor
- George Huff - Self
- Stevie Wonder - Self - Guest Performer
- Barry Manilow - Self - Guest Judge
- Shakira - Self - Guest Performer
- Kenny Rogers - Self
- Heather Locklear - Self
- Martina McBride - Self - Guest Performer
- Jon Bon Jovi - Self - Guest Performer
- Kellie Pickler - Self
- Reese Witherspoon - Self
- Ryan Starr - Self
- Lamont Dozier - Self - Guest Judge
- Olivia Newton-John - Self - Guest Judge
- Verdine White - Self - Guest Judge
- Lionel Richie - Self - Guest Judge
- Billy Joel - Self
- Diane Warren - Self - Guest Judge
- Neil Sedaka - Self - Guest Judge
- Robin Gibb - Self - Guest Judge
- Elton John - Self - Mentor
- Jason Priestley - Self
- Mark McGrath - Self - Guest Judge
- Camile Velasco - Self
- Gene Simmons - Self - Guest Judge
- LL Cool J - Self - Guest Judge
- Queen Latifah - Self
- Rod Stewart - Self - Guest Performer
- Tori Spelling - Self
- Ace Young - Self
- Melissa Gilbert - Self
- Rebecca Romijn - Self
- Clive Davis - Self
- Todd Bridges - Self
- Meat Loaf - Self - Guest
- Chris Daughtry - Self
- Jewel - Self - Guest Judge
- Anita Barone - Self
- Robin Thicke - Self - Performer
- Andrew Lloyd Webber - Self - Mentor
- Bette Midler - Self
- Katharine McPhee - Self - Guest Performer
- Céline Dion - Self
- Natasha Bedingfield - Self - Performer
- Graham Nash - Self - Performer
- Rihanna - Self - Performer
- Diana Ross - Self - Guest Performer
- Fergie - Self
- Nikki McKibbin - Self
- Kenny G - Self - Guest
- David Foster - Self - Guest Performer
- Amaury Nolasco - Self
- Jerry O'Connell - Self
- Gavin DeGraw - Self
- Daniel Powter - Self
- Mary J. Blige - Self - Guest
- LeBron James - Self
- Pink - Self
- John Legend - Self
- David Cook - Self
- LaToya London - Self
- Christina Christian - Self
- Kelly Clarkson - Self - Guest
- Kelly Clarkson - Self
- Sasha Cohen - Self
- Jeri Ryan - Self
- Mandy Moore - Self
- Burt Bacharach - Self - Guest
- Doug E. Fresh - Self
- Eli Manning - Self
- Andrea Bocelli - Self - Guest Performer
- EJay Day - Self
- Lulu - Self
- Lulu - Self - Guest Performer
- Christina Applegate - Self
- Al Jarreau - Self - Guest
- Micky Dolenz - Self
- George Michael - Self - Performer
- Bo Bice - Self
- Bo Bice - Self - Guest
- Barry Gibb - Self
- Barry Gibb - Self / Guest Performer
- Gladys Knight - Self
- Gladys Knight - Self - Guest Judge
- Taylor Hicks - Self
- Jim Verraros - Self
- Dolly Parton - Self - Guest / Mentor
- Dolly Parton - Self - Guest Performer
- Kimberly Caldwell - Self - Guest Host
- Jimmy Kimmel - Self - Performer
- Jane Kaczmarek - Self - Audience Member (uncredited)
- Neil Diamond - Self - Mentor
- Neil Diamond - Self - Performer
- Diana DeGarmo - Self
- Dionne Warwick - Self - Guest
- Jordin Sparks - Self - Performer
- Jordin Sparks - Self
- Marc Anthony - Self
- Annie Lennox - Self
- Paul Anka - Self - Guest
- Fantasia Barrino - Self
- Prince - Self - Guest
- Matt Damon - Self
- Jesse Spencer - Self
- Guy Sebastian - Self - Audience Member (uncredited)
- Joel Madden - Self
- BeBe Winans - Self
- Gwen Stefani - Self
- Gwen Stefani - Self - Guest Performer
- Peyton Manning - Self
- Tony Bennett - Self
- Tony Bennett - Self - Guest Star
- Ben Stiller - Self
- Helen Mirren - Self
- John McCain - Self
- Peter Noone - Self
- Peter Noone - Self - Guest Performer
- Wolfgang Puck - Self
- Helena Bonham Carter - Self
- Brad Pitt - Self
- CeCe Winans - Self
- David Boreanaz - Self
- Smokey Robinson - Self - Guest Judge
- Smokey Robinson - Self
- Kevin McNally - Self
- Clay Aiken - Self - Guest Host
- Clay Aiken - Self - Audience Member
- Clay Aiken - Self - Guest
- Harvey Weinstein - Self
- Hillary Clinton - Self
- Hugh Grant - Self
- Henry Winkler - Self - Audience Member (uncredited)
- Shaquille O'Neal - Self
- Ray Romano - Self - Interviewee / Audience Member
- Kyle Gass - Self
- Robin Williams - Ivan 'Bob' Poppanoff the 'Russian Idol'
- Sharon Osbourne - Self - Interviewee / Audience Member
- Keira Knightley - Self
- Kiefer Sutherland - Self
- Josh Groban - Self
- Snoop Dogg - Self
- Parminder Nagra - Self
- Carrie Underwood - Self
- Carrie Underwood - Self - Guest
- Jennifer Hudson - Self
- Jennifer Hudson - Self - Musical Guest
- Chris Kattan - Self
- Twiggy - Self
- Seal - Self
- Seal - Self - Performer
- Bono - Self
- Ewan McGregor - Self
- Hugh Laurie - Self
- Sarah Michelle Gellar - Self
- Rob Lowe - Self
- Jason Biggs - Self
- Forest Whitaker - Self
- Phil McGraw - Self
- Antonio Banderas - Self
- Tom Cruise - Self
- Rob Schneider - Self
- Goldie Hawn - Self
- Lisa Kudrow - Self
- Gwyneth Paltrow - Self
- Benji Madden - Self
- Gillian Anderson - Self
- Teri Hatcher - Self
- Eric McCormack - Self
- Bernadette Peters - Self
- Jack Black - Self
- Kevin Bacon - Self
- Lady Gaga - Self
- Emily Blunt - Self
- Kenny Loggins - Self - Guest Judge
- Kenny Wayne Shepherd - Self - Guest
- Matthew Rogers - Self
- Ruben Studdard - Self
- Ruben Studdard - Self - Audience Member
- Ruben Studdard - Self - Guest
- Kimberley Locke - Self
- Kimberley Locke - Self - Guest Performer
- Todrick Hall - Self - Contestant
- Todrick Hall - Self
- Katie Stevens - Self
- Katie Stevens - Self - Contestant
- Amy Adams - Self
- Tamyra Gray - Self - Guest
- Eric Anthony Lopez - Self - Auditionee
- Antonella Barba - Self
- Kristin Adams - Self
- Bruce Gowers
- Louis J. Horvitz
- Nigel Lythgoe
- Ken Warwick
- Norm Betts
- Theodore Dimitriou
- Simon Jones
- Katie Fennelly
- Melanie Oberman
- Brian Robinson
- Graham Barclay
Helena Bonham Carter hace el papel de Self.
Ellen DeGeneres interpreta a Self - Judge en la serie.
Brad Pitt interpreta a Self en la serie.
Antonio Banderas interpreta a Self en la serie.
Rob Lowe interpreta a Self en la serie.
Kiefer Sutherland interpreta a Self en la serie.
Matt Damon interpreta a Self en la serie.
Robin Williams interpreta a Ivan 'Bob' Poppanoff the 'Russian Idol' en la serie.
Reese Witherspoon interpreta a Self en la serie.
Keira Knightley interpreta a Self en la serie.
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