Missy Cooper

Missy is Sheldon's fraternal twin sister, who is a direct opposite of her brother in many ways (she is attractive, female, not above physical confrontation, and retains her southern accent). When Leonard, Howard, and Raj find out Sheldon has a sister and that she is quite attractive (The Porkchop Indeterminacy), they fall over each other trying to get her attention. Raj seems to be the only one who was partly successful in this endeavor. Missy finds more of an ally with Penny, who has become slightly immune to the quartet's geekiness, and helps Missy extricate herself from them.


 * Calls Sheldon by his nickname "Shelly"
 * Had her Easy-Bake Oven turned into a furnace for baking silicon substrates for homemade integrated circuits to make a robot to defend his room from her.
 * Tells people Sheldon is a "rocket scientist", which insults him because he is a theoretical physicist, which he views as much more prestigious.