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 Joshua Malina President Siebert Guest Star Sean Astin Dr. Pemberton Guest Star Kal Penn Dr. Campbell Guest Star Kip Thorne Himself Guest Star George Smoot Himself Guest Star Frances H. Arnold Herself Guest Star Chuck Lorre Executive Producer Bill Prady Executive Producer Steven Molaro Executive Producer