Mary Cooper is Sheldon's devout Christian mother whom Leonard Hofstadter describes as Sheldon's kryptonite because she is the only one able to control him. She is often unintentionally politically incorrect. Sheldon describes her as a kind, loving, religiously fanatical right-wing Texan, with a slightly out of scale head and a mild Dr. Pepper addiction. Background: She is also mother to Sheldon's twin, Missy, and his older brother, George Jr. She knew she had an unusual child in Sheldon and he frequently notes, I'm not crazy. My mother had me tested. She used to sing Soft Kitty to Sheldon when he was sick as a child.