A sitcom with tons of laughs and giggles is the perfect thing for anyone looking for comedic relief. And a diverse set of characters with varying characteristics and personalities is practically the icing on the cake. That's exactly why The Big Bang Theory was such a hit and continues to be a fan-favorite, long after the final season came to an end.
Each of the main characters had unique traits that set them apart from the others; from a particular style of dressing to a preferred haircut/hairdo, and unmatched idiosyncrasies. Some of these evoked sympathy from the audience while others were simply annoying. Fans loved them all the same, regardless of whether they were displaying the best of themselves or the worst.
Leonard: Pushover But Selfless
Leonard was part of the show from day one, right until the end. In all that time, he exhibited a lot of unique traits, the worst of which was jokingly listed by his friends in season 9's "The Sales Call Sublimation" when Penny asked him to set up an appointment with a therapist so he could help market the drug she was selling. He was a pushover, which is true of Leonard based on him almost always giving into what others want, failing to stand up for himself, and putting his own needs on the backburner.
However, that also meant he was selfless and willing to make great sacrifices for the people he cared about. Whether he was trying to keep Penny happy or putting Sheldon's many, unreasonable needs ahead of his own, he was always a friend indeed, ready to help out anyone in need.
Sheldon: Condescending But Intelligent
As one of the smartest people on the show, Sheldon had a tendency to look down on those he considered not to be at his intellectual level. In other words, everyone. Nary an episode passed without a condescending remark from Sheldon to any one of his friends. Howard, especially, suffered the brunt of this because, unlike the rest of his friends, he didn't have a doctorate.
His intelligence was also his best trait and what made him truly remarkable. He achieved a lot at a very young age and by the end of the show, he had a Nobel in Physics to show for his ingenuity. His intellect also brought him and Amy together, making the two one of the best couples of the show.
Howard: Insensitive But Devoted
One of the show's highlights was Howard's wit and humor, which never failed to leave the audience in stitches. But deep down, a lot of Howard's sarcastic remarks were hurtful and insensitive. He especially made fun of Raj, his best friend, which makes it so much worse.
Although he started the show as a pervy man, obsessed with women, Howard evolved into a mostly decent man when he met, dated, and married Bernadette. He became more mature and devoted to being a good husband and a better father to his children than his own was to him. From time to time, he even had some wise words to share with his friends.
Rajesh: Desperate But Sentimental
Of all the characters, Rajesh had the saddest love story, which especially sucked because he was so in love with the idea of love. His obsession with love bordered on desperation, leading to some ill-advised decisions like almost entering a sham of a marriage with Lakshmi because he was worried no one else would want to marry him or almost following Anu out of the country because he didn't think anyone else would love him.
Raj's sentimentality made him one of the sweetest guys in the group. He was a sincere, kind person who cherished his friends immensely. His friendship with Howard was proof of this as the two were part of major moments in the other's life.
Penny: Judgemental But Patient
When the show first started, Penny wasn't exactly shy about relentlessly making fun of her friends, whether it be Sheldon, Leonard, Howard, and Raj's love for all things video games and comic books or talking smack about Bernardette behind her back after she got her a job. All in all, Penny has a knack for being a tad mean and judgemental towards other people.
However, the amount of patience Penny exhibited wasn't talked about enough. She was one of the few people who could tolerate and understand Sheldon, for example—a feat requiring a great amount of patience in itself—to the point of listening to him talk about String Theory, which she didn't know or understand. On several occasions, she talked him down from a tantrum and catered to his wildly unreasonable needs when he was sick.
Amy: Clingy But Kind
As someone who grew up without any friends, Amy was quite desperate to be loved when she joined the group. She was especially attached to Penny, copying some of her behaviors, like drinking, just so Penny would like her. This particular trait led to a lot of changes to her character and even some crazy acts to get Sheldon's attention.
One of Amy's best traits was her kindness, which she extended to her friends and even people who were outside her circle. She was even kind to both Bert and Stuart who were socially awkward and almost always being picked on by others. Plus, she always had a kind word of advice or encouragement whenever her friends needed it.
Bernadette: Competitive But Protective
Bernadette's competitive streak didn't come out very often, but when it did, it was something to behold. It transformed her from the sweet, adorable lady fans knew and loved into a mean girl that no one would want to cross. Season 7's "The Scavenger Vortex" showed this side of Bernadette perfectly when she basically tortured Leonard (who was her teammate) as they competed with their friends to win.
Apart from competitions, Bernadette channeled her fierceness into protecting the people she cared about. She was very protective of Howard, especially, always defending him from Sheldon's taunts. She also defended Stuart when another comic book store owner was making fun of him.
Stuart: Timid But Caring
Although most of the main male characters in The Big Bang Theory were shy and socially awkward, most of them outgrew this by the time the show ended. Stuart, however, was not so lucky and he continued to be the shy, timid man fans loved and pitied. It was so bad that when his girlfriend suggested moving in together, he hid and ran away from her rather than tell her he wasn't ready and was afraid to ruin what they had.
Stuart grew closer to Bernadette and Howard when they offered him a place to stay when he had nowhere to stay. He, in turn, watched and took care of their kids and occasionally helped around the house, taking away a lot of the stress and pressure of parenthood.
Mary: Judgemental But Nurturing
Before her more present role in Young Sheldon—the spinoff of The Big Bang Theory—Mary Cooper made a number of appearances on the parent show. She always had an opinion on the religion, dressing style, and lifestyle of others; and while those were often accompanied by humor, they were, frankly, quite judgemental.
Despite her judgemental nature, Mary was a wonderful mother. She was kind and patient with Sheldon when he needed it, but also firm and strict when it was necessary. Her nurturing nature even extended beyond Sheldon to his friends when he'd visit them, make a home-cooked meal, and give them great advice.
Beverly: Indifferent But Honest
A big part of Leonard's story was his complex relationship with his mother who was always critical of him and rarely ever acknowledged his accomplishments. She often favored Sheldon over Leonard, which frustrated him to no end and only served to further increase the distance between them.
One of the few good things about Beverly was her honesty, even when people didn't want to hear it. She never minced words and her honesty helped the other characters grow stronger and become better.