Sheldon's oft-repeated habit of offering a hot beverage to a distressed house guest is apparently something that his mother taught him.
The writers have Mary Cooper talk of "Doctors change their minds, bacon is good one week and bad the next" in order to depict her Zack caliber ignorance of science. However in the 1950s doctors really would recommend a daily spoonful of lard or bacon fat (or corn oil) to prevent essential fatty acid deficiency (a serious problem with babies being bottle fed low fat infant formula).
Mary Cooper notes that Indian people may also be prejudiced against white people. In The Electric Can Opener Fluctuation (2009), Raj visited Texas, and was indeed surprised not to see any Texas western tropes such as saloons, tumbleweeds and cattle drives.
Mary Cooper uses the term "a hoot and a half" to describe a Christian-themed cruise she is about to take. In The Electric Can Opener Fluctuation (2009) just after Leonard, Howard and Raj complain about the guys' recent Arctic trip, Sheldon says it was "a hoot and a half".
Mary confirms that Sheldon was tested for insanity as a child and the doctor said he was fine. She does regret, however, about not taking him to a follow-up specialist in Houston.