Missy Cooper, Sheldon's sister, made a significant impression on The Big Bang Theory despite appearing only twice. Young Sheldon showcases Missy's unique qualities, such as street smarts and emotional maturity, proving she is the odd Cooper sibling. The Big Bang Theory missed a great narrative opportunity by barely featuring her, particularly in regards to Missy meeting Amy, Sheldon's wife. CBS had no idea Missy would become so popular on Young Sheldon, and the distant relationship between Sheldon and Missy in the original show explains why she was rarely included. Incorporating Missy and her family in the later seasons of The Big Bang Theory was already difficult.
