 Several of the actors in "The Big Bang Theory" previously worked together on the sitcom "Roseanne", including Johnny Galecki, Sara Gilbert, Laurie Metcalf (who plays Sheldon's mother, Mary Cooper), and Meagen Fay (who plays Bernadette's mother).Additionally, Lorre was a writer on the series for several seasons.David Saltzberg, a professor of physics and astronomy at the University of California, Los Angeles, checked scripts and provided dialogue, mathematics equations, and diagrams used as props.