Prickly, pedantic, humorless, narcissistic, and helpless in the face of many commonplace tasks: Dr. Sheldon Cooper begins The Big Bang Theory with many a mark against him. Yet it is these very qualities that make him so endearing a character, so singular a presence on the silver screen, and without those crushing limitations, he would have nowhere to grow.
Though his stubbornness can often seem an immovable object, it is pushed throughout the series by an unstoppable force: friendship. Sheldon may not wish to change or even see the need to, but change he does, and almost every time it happens it is because his friends fought to bring forth a better Sheldon, like sculptors coaxing a statue out of marble.
10 Sheldon Drives
Who will drive Sheldon to the comic book store, the train store, Caltech, or on any number of disagreeable errands? This question looms over many episodes early in The Big Bang Theory, because Sheldon doesn't drive.
His incessant badgering of his friends, in particular Leonard, to drive him to and fro is a free joke generator, and things only get funnier when the truth about his unwillingness to drive comes out. Sheldon receiving his license represents increased independence and a step out of his permanent childhood, though it means no more "airbag" pillows to the face during driving simulations.
9 Sheldon Makes New Friends
Early on, Sheldon's only friends are Leonard, Howard, and Raj, and if pressed Sheldon would likely say that Howard and Raj are expendable. Yet due to Leonard's nagging influence and, more importantly, Penny's attempts to loosen Sheldon up, Sheldon slowly and begrudgingly makes other friends.
Amy, Bernadette, Stuart, and even former nemesis Wil Wheaton all enter his social orbit, and though these friendships are burdened by near-constant gaffes and insults from a man oblivious to the needs of others, they are friendships that outlast every storm. Sheldon's new sociability might have been met with mixed reviews, but it grew the character like little else.
8 Sheldon Respects The Other Sciences
Sheldon looks down on geology, biology, and virtually every scholastic subject except physics, because in his mind only theoretical physics is "real" science. His ego clings to this view of physics for a long time.
At last, however, learning more about the work of microbiologist Bernadette, neurobiologist Amy, and even geologist Bert taught Sheldon that while he may love physics most, the other subjects are not without their merits, nor are the scientists who have devoted their lives to their study. Sheldon might appreciate geology little more than he does Penny's stylish wardrobe, but at least now there is a layer of respect beneath his jabs.
7 Sheldon Moves Out
The apartment he shares with Leonard is precious to Sheldon. At least, his spot on the couch is precious to him. The running joke of Sheldon's spot could've carried any great comedy. Other than the train store and Stuart's comic book shop, there are few places where Sheldon feels comfortable, and none more so than in his apartment.
Leonard, Penny, and Amy scarcely dream that Sheldon will feel comfortable living elsewhere, and yet with time, gentle persuasion, and a bit of deception, they eventually wear him down, and in the end, Sheldon is happy they did. Moving away from Leonard, even if it is just across the hall, in some ways marks the last great step towards maturity for Sheldon, which may be why he resented it so much.
6 Sheldon Loosens Up About Rules
Sheldon is most comfortable when dictating every last detail of his life with a dictator's iron fist, hence "the Roommate Agreement": half-legalese, half-neurosis, 100% the bane of Leonard's existence. Whistling in the apartment is forbidden.
One must stand only so close to the mirror when brushing one's teeth. Bathroom time is scheduled. It's enough fodder for a comedy special. Of all the changes that Sheldon undergoes, his loosening up about rules might be the greatest gift to those around him, in particular Leonard, who for years suffered through Sheldon at his most nitpicky and pedantic. Though Sheldon never becomes the spontaneous spirit that Howard is, he does relax.
5 Sheldon Switches To Dark Matter
Before Sheldon loved Amy Farrah-Fowler he loved string theory. His obsession with the subject is so absolute that everyone, including him, is convinced that he will likely one day win a Pulitzer for his research. No one is more surprised or upset than Sheldon himself when stagnant research forces him to shift his professional trajectory to dark matter, jeopardizing everything he's worked for since childhood.
Though the shift is dramatic and the consequences are at first severe, opening his eyes to new possibilities turns out to be exactly the kind of shakeup Sheldon needs, and by turning toward new scientific horizons, Sheldon is able to make the scientific leap that he had only dreamed of with string theory.
4 Sheldon Develops A Sense Of Humor
It is not a coincidence that Sheldon adores Spock. To him, the Vulcans are the embodiment of scientific detachment: dispassionate, objective, and humorless. During Leonard's interview as a prospective roommate, Leonard cracks a joke, and Sheldon marks it down as a strike against him.
Then came the Age of Bazinga, when the badgering of his friends wore away his stoic exterior, and the jokes and pranks flooded forth. Sheldon's humor might be too dry, arch, or gently scolding for some, and might not match Seinfeld's best humor, but he proves himself to be a wellspring for comedy, even intentional comedy, once he's set his mind to being funny.
3 Sheldon Appreciates His Friends
Leonard, Howard, Raj, and Penny bring much to Sheldon's life. Even the couch and therefore Sheldon's precious "spot" only exist because Leonard purchased it, yet early in the series Sheldon is oblivious to the constant, giving gestures and support of his friends.
It takes a long time for the wall to crack and Sheldon to show his appreciation for those that enrich his life, but in time Sheldon realizes that without Leonard and the others, his life would be barren. His meeting with an eccentric mathematician who has chosen self-imposed exile shows Sheldon just how grateful he is for his friends, even if that won't stop him from complaining.
2 Sheldon Opens Up Emotionally
Emotionally stunted would be a generous description of Sheldon in the early episodes. From the first time the opening theme plays until the finale, his friends regularly compare him to a robot for his almost total emotional disconnect, a disconnection that regularly leads to him hurting the feelings of those around him.
Leonard, Wil Wheaton, and the university HR rep are only a few of the targets of Sheldon's careless sniping. By the end of the series, Sheldon has gained a significant appreciation for the way that his words and actions affect those around him. He is at last well enough in touch with his feelings to be able to express his needs and empathize with others.
1 Sheldon Falls In Love
Howard and Raj might have brought Sheldon Cooper and Amy Farrah-Fowler together, but what kept them together was love, a feeling that no one thought Sheldon possessed. Their courtship might have made tortoises look like the Flash, but advance it did. From its robotic beginning to awkward flirtation, the first, tender touches, and their eventual union, nothing changed Sheldon more dramatically than falling in love with Amy.
Not only did their romance require him to open up emotionally, but it also required him to get over his fear of germs, physical contact, and intimate social situations. That Sheldon would overcome some of his worst fears in the name of loving Amy is a testament to how much he changed, and how worth it that change was.