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 Billy Bob Thornton Dr. Oliver Lorvis Guest Star Chuck Lorre Executive Producer, Writer Bill Prady Executive Producer Steven Molaro Executive Producer, Writer Eric Kaplan Writer Jim Reynolds Writer Steve Holland Writer Maria Ferrari Writer Mark Cendrowski Director