Sheldon Lee Cooper is an imperious, uber-nerd genius totally lacking in social skills who is a theoretical physicist at the California Institute of Technology. He has been the roommate of fellow nerd Leonard Hofstader for several years when the series begins. Sheldon is the smartest person he knows and frequently reminds people of this. Even his friends have to hear why they are inferior to him. He is a creature of routine and becomes distressed when his comfortable world is upset. He does not drive, but expects others to give him rides like it's their job.
He cannot let someone misspeak without being corrected and he is fond of long, belabored explanations and speechifying.
He does not have a typical sense of humor, and often misses out on the subtlety of sarcasm or irony, but occasionally cracks himself up and is a fan of pranks, which he punctuates with a "Bazinga!"
He is aware that others seem him as a nerd, but he has very little time for what others think of him, since he's smarter than them. He also keeps track of when he feels wronged by people, assigning "strikes," after three the offender has the choice to apologize, be banished from his apartment for a year or take a class.
He has a preferred spot on the couch and will not sit anywhere else. His friends have found it's easier to let him have his way than try to convince him otherwise. He always says his neighbor Penny's name and knocks three times when he goes to her apartment. Penny enjoys aggravating Sheldon by taking his spot on the couch or other small tweaks to his routine, but they eventually become friends.
He shows no interest in romantic or physical relationships, even when he eventually ends up with a girlfriend, Amy Farrah Fowler.
Background: He was born in Galveston, Texas in 1980. His mother, Mary Cooper, is extremely religious and his father George died when Sheldon was young due to health problems related to his weight. He has an older brother named George Jr. and a twin sister named Missy, who do not share their brother's intellect.
He was bullied constantly as a child and conducted frequent science experiments, many of which resulted in minor damage or bodily injury.
When he is sick he reverts to a childlike state and insists on being taken care of, which includes Penny singing him "Soft Kitty."
He has a Bachelor of Science, Master of Science, Master of Arts, Ph.D. and Doctor of Science.
He started college when he was 11 and received his first Ph.D when he was 16. His current field of study is on string theory and M-theory, and he has an interest in high energy colliders and nuclear fusion.
He has a photographic memory and is keenly interested in hygiene. He does not do drugs or drink, even caffeine.
He claims actor Wil Wheaton is his arch enemy ever since the actor failed to show at an autograph event that Sheldon traveled 10 hours by bus to reach. They have several encounters in which "evil" Wil Wheaton confirms Sheldon's hatred.
He is a fan of comic books, Star Wars, Star Trek (he speaks Klingon), Battlestar Galactica and Doctor Who, but hates Babylon 5.
His IQ is 187, although he claims tests don't accurately measure his intelligence.