Missy Cooper is Sheldon Cooper's fraternal twin sister in The Big Bang Theory and its prequel Young Sheldon, portrayed by Courtney Henggeler (adult) and Raegan Revord (younger). She is known as the more socially adept and athletic twin, often contrasted with Sheldon's intellectual focus, and her life is explored in detail in Young Sheldon, showing her struggles and eventual growth into a successful adult with a family, despite facing personal challenges. 