Jessica Lange, Melissa Rycroft and Tony Dovolani, Ludacris and Jesse McCartney

Episode 1

Episode 18

Nicollette Sheridan/The All-American Rejects

George Clooney/Kiefer Sutherland/T.I.

Amy Poehler, James Morrison

Joey Fatone, O.A.R.

Ted Danson, Ernie Bjorkman

Kevin Nealon, Chris Harrison

Alyson Hannigan, Brandon Wilson

Heidi Klum, Justin Long, Marco Borges

Josh Brolin, Pink with Butch Walker

Penelope Cruz, Dylan and Cole Sprouse, Q-Tip

Jennifer Aniston, Stevie Wonder

John Mayer, Josh Groban, Lady Antebellum, Chester Pitts, Ephraim Salaam

Amy Brenneman, Jason Mraz and Colbie Caillat

Mel B, Eric Dane, Robin Tunney, Melinda Doolittle

Steve Harvey, Kurt Warner, Dr. Neil Shaw

John Legend, Jerry O'Connell

Simon Baker, Miranda Cosgrove

The Jonas Brothers, Mel B

Naomi Watts, Lily Allen

Jeff Probst, Nick Carter

George Lopez, Bar Refaeli

Meredith Vieira, Olivia Wilde

Richard Simmons, Serena Williams, Raphael Saadiq

Denise Richards, Chyler Leigh, Fabio Viviani

Mario Lopez, the Bird and the Bee

David Arquette, Fall Out Boy

Neil Patrick Harris, Kaley Cuoco

Judge Judy Sheindlin, Bret Michaels, Matt Nathanson

Eric McCormack, Chris Harrison, Anthony LaPaglia, the Fray

"The Bachelor" runner-up Melissa Rycroft, Kym Douglas

Jason Mesnick and Molly Malaney, Steve Spangler

Paris Hilton

Carla Gugino, Sean "Diddy" Combs, Taylor Hicks

Carol Burnett, Taylor Hicks

Felicity Huffman, Rascal Flatts

Dwayne "The Rock" Johnson, Elle Fanning

Portia de Rossi, "American Idol" castoffs Jorge Nunez and Jasmine Murray

Julia Louis-Dreyfus, Andy Samberg

Zach Braff, Jenna Fischer

Anderson Cooper, Katy Perry

Paul Rudd, Gavin Rossdale, 7-year-old golfer Brett Sodetz

Noah Wyle, "American Idol" castoff Alexis Grace

Kara DioGuardi, M.C. Hammer

John Stamos, Emily Blunt

Jennifer Hudson

Reese Witherspoon, Bobby Flay

David Spade, Gilles Marini and Cheryl Burke

Halle Berry, Flo Rida

Christina Applegate, Keith Urban

Howie Mandel, Ben McKenzie

Marilu Henner, Lil' Kim and Derek Hough, Martina McBride

Patricia Arquette, Wayne Hoffman, "Dancing With the Stars" castoff David Alan Grier, Rascal Flatts

Jenny McCarthy, Mary McCormack, Natasha Bedingfield

Zac Efron, Demi Lovato

Drew Barrymore, Barry Watson, the Pussycat Dolls

Leslie Mann, Rashida Jones, Pussycat Dolls

Jimmy Kimmel, Marilyn Milian, Brett Dennen, 7-year-old break-dancer Angelo Baligad

Jennifer Love Hewitt, Chicago

Lindsay Lohan, Alec Greven, Prince

Matthew Perry, Leighton Meester

Kristin Chenoweth, "American Idol" castoffs Anoop Desai and Lil Rounds

Kate Walsh, Dierks Bentley, child solar-system expert Brandt Bickford

Michael Douglas, Faryl Smith

Ryan Reynolds, 7-year-old piano prodigy Emily Bear

Matthew McConaughey

Heidi Klum, Annie Duke, "American Idol" castoff Matt Giraud

Simon Cowell, Zachary Quinto, the Black Eyed Peas

Hugh Jackman, Chris Pine

Vanessa Hudgens, 11-year-old sport stacker Steven Purugganan, Kym Douglas

Ryan Seacrest, Alison Sweeney

Jon Cryer, "American Idol" castoff Allison Iraheta, Alison Sweeney

Matthew Fox, Julianne Moore, Lady GaGa

Jay Leno, Ciara

Anderson Cooper, Kelly Clarkson

Ewan McGregor, the winner of "The Biggest Loser", Pink

Jamie Foxx, Marisa Miller, piano prodigy Umi Garrett

George Lopez, No Doubt

Ben Stiller, David Cook

Kevin Nealon, Tamar Geller, Michael Johns

Queen Latifah, Wayne Dyer, Rob Thomas

Steve Martin

Mandy Moore, Kris Allen

Jessica Biel, Kathy Freston, Kellie Pickler