Bernadette Maryann Rostenkowski-Wolowitz, PhD (portrayed by Melissa Rauch ; main: seasons 4–12; recurring: season 3) is originally a waitress and co-worker of Penny's at The Cheesecake Factory, using her wages to pay for her graduate studies in microbiology. She is a smart, short-tempered, ruthless, competitive young woman. Despite her short stature and squeaky voice, she is regarded as being intimidating, largely because of her sharp tongue, aggressive demeanor and tendency to be a bully. A recurring joke in the series references Bernadette and her lab team handling dangerous or infectious specimens, leading to accidental byproducts.