In season 10, Sheldon moves across the hall with his girlfriend Amy Farrah Fowler (Mayim Bialik), in the former apartment of Leonard's wife Penny (Kaley Cuoco).

[8] He has a genius-level IQ of 187, however he displays a fundamental lack of social skills, a tenuous understanding of humor, and difficulty recognizing irony and sarcasm in other people, although he himself often employs them.

[19] Sheldon and his fraternal twin sister, Missy, were born on February 26, 1980, at Lawrence Memorial Hospital in Galveston, Texas,[20] and raised in Medford, a fictional small town in East Texas that is a three-hour drive from Dallas, along with their older brother, George Jr., by their mother, Mary Cooper, an overtly devout Baptist, and their father, George Cooper Sr., a football coach.

The only member of his family to have actively encouraged his work in science was his maternal grandfather, whom he cherished and affectionately called "Pop-Pop", and who died when Sheldon was five years old.

Sheldon was interested in science from an early age, and was a child prodigy,[26] although due to his behavioral quirks and his lack of humility about his superior intellect, he was bullied by classmates and neighbors.

[28] Throughout the entire run of The Big Bang Theory, the college he went to for undergraduate studies had not been revealed, but he always felt it was superior to his fellow Big Bang Theory colleagues' alma maters of Princeton (Leonard), Cambridge (Raj), MIT (Howard) and Harvard (Amy); however, it is implied in "The Tam Turbulence" (Season 12, Episode 4) that Sheldon is in fact a Caltech alumnus, and in Young Sheldon he is said to enroll at the fictional East Texas Tech before finally enrolling at Caltech in the final episodes of the series.

From then, he worked on his doctorate, was a visiting professor at the University of Heidelberg in Germany, was the youngest person at the time to receive the Stevenson Award,[5] and has appeared on the cover of Journal of Physical Chemistry A.

Like Leonard, Raj, and Howard, Sheldon is characterized as being highly intelligent, but he tends to display childish qualities, such as extreme stubbornness and meanness.

[35][36] Sheldon possesses a mastery (and extensive knowledge) of various subjects such as physics, spectroscopy, radiology, chemistry, pharmacology, both anatomy and physiology, zoology, microbiology, astronomy, cosmology, algebra, geometry, calculus, trigonometry, economics, computers, software engineering, robotics/cybernetics, artificial intelligence, nanotechnology, history, anthropology, geography, linguistics, cryptography, forensics, and railroad engineering (he is a well-known railfan and a fancier of model trains), and in addition to being fluent in Klingon, has some knowledge of Swedish,[37] Finnish, Mandarin,[38] and Hindi.

", which is now an officially registered trademark of Warner Bros.[41][42] He is uncomfortable with human physical contact and has mysophobia, which makes his exceptionally rare hugs extremely awkward and painful-looking.

In his mannerisms, Sheldon also shows symptoms associated with obsessive-compulsive personality disorder, as is suggested within the show itself by Amy in regard to how, whenever approaching the door of an occupied room—say the bathroom—he must knock three times, then say the person's name, and must repeat this three times; this was revealed as a result of him seemingly walking in on his father with another woman (although in reality it was just his mother roleplaying) when he was thirteen ("The first [knock] is traditional, but 'two' and 'three' are for people to get their pants on.").

Sheldon has restraining orders from his heroes Leonard Nimoy, Carl Sagan, and Stan Lee,[49][50][51][52] as well as television scientist Bill Nye.

His father George died before the start of The Big Bang Theory, when Sheldon was 14, [65] while his mother Mary is a devout Baptist and loving parent.

Sheldon has two siblings: a twin sister, Missy, who is a tall, attractive brunette as an adult; and an older brother,[66] George Jr., who owns a tire store chain headquartered in Dallas called Dr.

In The Big Bang Theory, Sheldon did express an interest in having children with Amy, albeit an unfeasibly large number in order to serve as subjects for social or behavioral experiments.

Of the three, Sheldon is openly dismissive of Howard and constantly opines that a master's degree in engineering demonstrates a lesser intellect than that of the others, who all possess science doctorates.

[73] Sheldon can only handle having a limited number of friends in his life at a time, but later shows flexibility when he accepts Bernadette and Amy as part of the social group.

[76] While some fans supported a romantic relationship between Sheldon and Penny,[77][78] Lorre stated his opposition to it by saying: "We've stumbled into creating a character who has chosen a lifestyle for himself that is unique.

Series co-creator Chuck Lorre said: "Part of what's wonderful and unique about [Sheldon] is he has chosen not to play in the relationship game either way  – heterosexual, homosexual, bisexual, any sexuality.

After some obnoxious comments about the dating website, Sheldon finds that Amy agrees with him, and he grows fond of her when she says that "Any or all physical contact up to and including coitus are off the table".

[84] During the first half of season 6, in "The Parking Spot Escalation" and "The Fish Guts Displacement", Sheldon is pushed further after seeing Amy partially exposed and taking care of her while she is ill respectively.

In "The Platonic Permutation" Amy offers Sheldon a chance to get back together with her after spending time together in an aquarium at Thanksgiving, but learns that he simply just wants to be her friend, with him revealing to her that "I excel at many things, but getting over you wasn't one of them".

In the following episode, "The Opening Night Excitation" Leonard, Howard and Raj go to see Star Wars: The Force Awakens without Sheldon as while he was initially reluctant, ultimately opted to celebrate Amy's birthday with her instead.

To make Amy's birthday enjoyable and memorable, Sheldon seeks out Penny and Bernadette as he respects their opinions regarding all things socially appropriate.

He reveals to them that he has narrowed things down to three options, the first being a chance to play the harp with the Los Angeles Philharmonic, the second being an all-expense-paid trip to the Wisconsin Sheep and Wool Festival (though Amy would have to go alone because Sheldon's ornithophobia is nothing compared to his fear of sheep), and the third being the two of them engaging in coitus, at which point Penny squeezes and shatters the wine glass in her hand due to disbelief and/or shock.

In the tenth-season finale, Sheldon unexpectedly proposes to Amy after being kissed by Ramona Nowitzki, a graduate student who had been infatuated with him in earlier seasons.

In the series finale, both Sheldon and Amy are recipients of the Nobel Prize in Physics for their discovery of super asymmetry which they first worked on moments before their wedding.

[88][89][90] James Chamberlin of IGN wrote: "It's hard to imagine what The Big Bang Theory would be if it weren't for Jim Parsons' great portrayal of Sheldon Cooper".

[97] On January 16, 2011, Parsons won the Golden Globe Award for Best Actor – Television Series Musical or Comedy, presented by co-star Kaley Cuoco, for his work on seasons 3 and 4.

He also stated that "the way his brain works, it's so focused on the intellectual topics at hand that thinking he's autistic is an easy leap for people watching the show to make".