Hostess at Fuddruckers
Missy Cooper is Sheldon's fraternal twin sister, who is the direct opposite of her brother in many ways (besides being a female, she is not above physical confrontation, is very charming and amicable, as well as possessing a very cheeky sense of humor).
Missy's main appearance is in "The Porkchop Indeterminacy" (S01E15). When Leonard, Howard, and Raj find out Sheldon has a sister and that she is quite attractive, they fall over each other trying to get her attention. Raj is inspired to begin taking an experimental medication to overcome his pathological shyness.
When Sheldon states that he'll decide who Missy dates (desiring that she reproduce with a smarter version of him, which he dubs "Sheldon 2.0"), she decides to speak with him privately. She tells him that she is fine with him acting like a brother who cares about her, but if he tries to tell her who to sleep with in her bed, they are gonna go "round on round" like they did when they were children. This flies over Sheldon's head and he suggests Missy donate her eggs and cryogenically store them until he finds the right sperm donor to fertilize them before implanting them into her body. By this act, he suggests, "everybody wins". Missy then begins painfully squeezing her brother's testicles until he withdraws the statements.
Missy finds more of an ally with Penny, who has become slightly immune to the quartet's geekiness, as well as helps Missy extricate herself from them and lets Missy hang out in her apartment. Leonard, Howard, and Raj all knock on Penny's door to ask Missy out, but all of them fail in the end.
Before she leaves, Missy tells Sheldon that she is proud and reveals that she brags to her friends about her brother "the rocket scientist", which sparks him to correct her that he's a theoretical physicist, noting the difference. After she leaves, Sheldon mutters back to his apartment saying that being a rocket scientist is beneath him.
In "The Cooper Extraction" (S07E11), Missy is about to give birth to a baby in Texas. Since her husband is recovering from a horrible motorcycle accident, Sheldon has to go back to look after her. Missy does not appear on screen in this episode, only a scream that is supposed to come out of her is heard.
- She calls Sheldon by his nickname, "Shelly", as does their mother.
- When they were kids, Sheldon turned her Easy-Bake Oven into a furnace for baking ceramic semiconductor substrates for homemade integrated circuits to make a robot to defend his room from her.
- Missy tells people Sheldon is a "rocket scientist", which insults him because he is a theoretical physicist, which he views as much more prestigious and tells her that she might as well tell people that he is a toll collector at the Golden Gate Bridge.
- Despite their differences, Missy is very proud of Sheldon, constantly bragging about her "brother the rocket scientist" to her friends.
- When Leonard offered Missy to stay with them, she reveals that Sheldon does not like company and he used to send his imaginary friends home at the end of the day when he was a child: he denies it, saying that they were "imaginary colleagues".
- When aggressively approached for a date by Sheldon's friends, Missy rejects Leonard and Howard. However, when Raj makes his attempt she recognizes that his medication has worn off, so she changes her tactic and says, "Hi, cutie pie, I was hoping you'd show up." His mutism predictably kicks in, driving him away.
- She once had a dog who made strange noises which she later had put down.
- It is revealed in the Pilot that she is a hostess at Fuddruckers when Sheldon is expressing concern of "committing genetic fraud" about donating sperm at a high-IQ sperm bank ("I have a sister who has the same basic DNA mix who hostesses at Fuddruckers.")
- Her full first name may be Melissa, as Missy is a common nickname.
- Her mother dismisses her as "dumb as soup" in "The Luminous Fish Effect": though she is likely nowhere near as intelligent as her brother, she seems witty, presentable, and funny. Though Sheldon also mentioned in "The Cooper Extraction," it took Missy six years to graduate from High School, implying her's mother's comment about her intelligence isn't wholly inaccurate.
- When she first meets the gang at Cal Tech, she tells them that she spent nine months with her legs wrapped around Sheldon's head.
- She used to obligate Sheldon to do whatever she wants by pressing his testicles. She still does it when she gets mad at him.
- Sheldon considers her, with his help in choosing a proper and approved-by-him mate, the future mother of a "Sheldon 2.0". She, however, doesn't see it that way.
- She is taller than Leonard, Penny, Raj and Howard, like her brother.
- In the episode The Cooper Extraction it's revealed that Missy is married and had a baby.
- Husband: Unnamed Sr
- Son: Unnamed Jr
- Father: George Cooper Sr.
- Mother: Mary Cooper
- Brothers: Sheldon Cooper, George Cooper Jr.
- Grandmother: Meemaw
- Grandfather: Pop-pop
- Uncles: Uncle Carl, Uncle Edward