Character mistake: When Sheldon is telling Leonard, Amy and Penny about how his voice is like a white James Earl Jones, he quotes the famous Darth Vader line "Luke, I am your father." This is an example of the Mandela Effect, that apparently even Sheldon Cooper is susceptible to. Darth Vader actually says "No. I am your father."
Character mistake: While bedridden after his vasectomy, Howard asks Bernadette to grill up a couple steaks instead of picking up Chinese for dinner. She gives him a disapproving look and he says "Kung Pao Chicken, please." A major ingredient of Kung Pao Chicken is peanuts. A major allergy for Howard is peanuts. (00:09:04)