Melissa "Missy" Cooper (Courtney Henggeler as an adult; guest: seasons 1 & 7 & 11 and Raegan Revord as a child, main: Young Sheldon) is not as academically accomplished as her twin brother but displays better social skills. As a child, she was obsessed with Alf. In season three of Young Sheldon, Missy joins the baseball team in the fictional town of Medford. While Sheldon finishes high school and matriculates at university, Missy navigates the ordinary challenges of adolescence. Despite their differences, the twins are pretty close; they are both atheists.