Johnny Galecki
Leonard Hofstadter (24 eps)
Jim Parsons
Sheldon Cooper (24 eps)
Kaley Cuoco
Penny (24 eps)
Simon Helberg
Howard Wolowitz (24 eps)
Kunal Nayyar
Rajesh Koothrappali (24 eps)
Melissa Rauch
Bernadette Rostenkowski (24 eps)
Mayim Bialik
Amy Farrah Fowler (24 eps)
Carol Ann Susi
Debbie Wolowitz (voice) (7 eps)
Kevin Sussman
Stuart Bloom (3 eps)
Brian Thomas Smith
Zack Johnson (3 eps)
Steve Wozniak
Self (1 eps)
George Takei
Self (1 eps)
Eliza Dushku
Angela Page (1 eps)
Rick Fox
Glenn (1 eps)
Jessica Walter
Mrs. Latham (1 eps)
LeVar Burton
LeVar Burton (1 eps)
Vernee Watson-Johnson
Althea (1 eps)
Phil Abrams
Dr. Bernstein (1 eps)
Ed Lieberman
Announcer (voice) (1 eps)
Katee Sackhoff
Self (1 eps)
Annie O'Donnell
Mrs. Fowler (1 eps)
Eric André
Joey (1 eps)
Arnold Chun
Ho-Jun (1 eps)
Tiffany Dupont
Angela (1 eps)
Charlotte Newhouse
Joy (1 eps)
Whitney Avalon
Elsie (1 eps)
Lanny Joon
Officer Shin (1 eps)
Sharon Omi
Nurse in Biohazard Suit (1 eps)
Tom Yi
Dispatcher (voice) (1 eps)
Brian Greene
Self (1 eps)
Chris Reed
Todd Zarnecki (1 eps)
Neil deGrasse Tyson
Neil deGrasse Tyson (1 eps)
Keith Carradine
Wyatt Teller (1 eps)
Wil Wheaton
Wil Wheaton (1 eps)
Joshua Malina
President Siebert (1 eps)