Mary Cooper

Mary Cooper is Sheldon Cooper's mother, a devout born-again Christian from East Texas. She has two other children, Sheldon's fraternal twin sister, Missy, and an older son named George Jr. Mary is not an intellectual like her son, but is very wise, caring and sweet-natured; she is very religious and, at times, can be unwittingly politically incorrect - something Leonard occasionally has to point out to her. She appears to be an extremely good mother and is the only one who has ever been able to control Sheldon. Leonard describes her as Sheldon's "Kryptonite".

She is called upon by both Leonard and Penny when Sheldon gets particularly difficult to handle. In particular, she was brought in to address:
 * Sheldon picking up random projects to consume his time after being fired. Mary initially tried to put him into a comfort zone in which he would be receptive to trying to get his job back and, when tired of waiting, forced Sheldon to apologize to Dr. Gablehauser.
 * Sheldon getting into a protracted dispute with Penny. After seeing the battle escalate several times, Leonard advised Penny to call Mary, who responded by ordering Sheldon to forgive and apologize to Penny.
 * Sheldon sinking into a depression after discovering his research data on the Arctic Expedition was faked. After Sheldon fled to her home in Texas, Mary convinced Leonard, Raj, and Howard to come to Texas and apologize and further convinced Sheldon to forgive them by calling evolution an "opinion".
 * Sheldon "sulking" after "breaking up" with Amy Farrah Fowler (including the purchase of 25 cats). After meeting with Amy, Mary uses reverse psychology to trick Sheldon into getting back together with Amy.

Sheldon describes Mary as being a "kind, loving, religiously fanatical, right-wing Texan, with a slightly out of scale head and a mild Dr Pepper addiction". Sheldon has also uses his Mother to exact the point that he isn't crazy, as she had him tested. Mary later confirmed the story, although with the caveat that she wished she'd "followed up with that specialist in Houston."

As shown in "The Rhinitis Revelation", Sheldon's friends are all very fond of her, mostly because she offers maternal help and advice that few of them - particularly Leonard - received from their mothers.

Trivia

 * Laurie Metcalf was a regular in the sitcom Roseanne, along with Johnny Galecki and Sara Gilbert.
 * Even though Mary does admits (as Sheldon often says) that he is not crazy because she did have him tested, she does wish she had him taken for further testing in Houston.
 * Both Sheldon and Leonard's mothers are fit for the other: Mary for Leonard and Beverly for Sheldon. Given how the Season 6 page states that the two mothers will meet and result in mother envy, you can expect them to point this out.
 * In "The Precious Fragmentation" Sheldon says she has a mild Dr. Pepper addiction. Her addiction to caffeine can be observed in "The Electric Can Opener Fluctuation" when she is seen drinking Pepsi.