Johnny Galecki Leonard Hofstadter Actor Jim Parsons Sheldon Cooper Actor Kaley Cuoco Penny Actor Simon Helberg Howard Wolowitz Actor Kunal Nayyar Raj Koothrappali Actor Mayim Bialik Amy Farrah Fowler Actor Melissa Rauch Bernadette Rostenkowski Actor Kevin Sussman Stuart Guest Star Laurie Metcalf Mary Guest Star Riki Lindhome Ramona Guest Star Stephen Hawking Self Guest Star George Wyner Dr. Zhang Guest Star Susan Chuang Dr. Harris Guest Star Chuck Lorre Executive Producer, Writer Bill Prady Executive Producer Steven Molaro Executive Producer Eric Kaplan Writer Jeremy Howe Writer Steve Holland Writer Maria Ferrari Writer Tara Hernandez Writer Mark Cendrowski Director