Johnny Galecki Leonard Hofstadter Actor Jim Parsons Sheldon Cooper Actor Kaley Cuoco Penny Actor Simon Helberg Howard Wolowitz Actor Kunal Nayyar Raj Koothrappali Actor Elizabeth Bogush Dr. Catherine Millstone Guest Star Oliver Muirhead Professor Laughlin Guest Star Elena Campbell-Martinez Maria Guest Star Chuck Lorre Executive Producer Bill Prady Executive Producer Steve Holland Writer Mark Cendrowski Director