Rajesh Koothrappali

Rajesh "Raj" Ramayan Koothrappali is Wolowitz's best friend and of course another genius. He is Indian, albeit he dislikes Indian food (as seen in The Luminous Fish Effect and in The Dumpling Paradox) and culture. He has a thick Indian accent and, like Wolowitz, a love for Stephen Hawking. Originally, He worked in the Physics department at Caltech, where his area of expertise is particle astrophysics. For his discovery of a planetary object beyond the Kuiper Belt (which he called "Planet Bollywood") he was included in People magazine's "30 Under 30" to watch, and thus received a larger office for his work, granting him some form of celebrity status. However, the work Raj performs at the University is repetitive enough that he could conceivably get replaced by a simple software program. But After, The Pirate Solution where Raj's research came to a dead end, when the University finds out he is not working anymore he will be deported, to avoid this Sheldon asks him to work for him, after several disputes he agrees.

Personality
Raj, being originally from India, is slightly clueless about the American culture, although he dislikes Indian food and his own culture. He is very sensitive to racist jokes, which he is frequently a target of. He also has selective mutism, a speaking disorder which renders him unable to talk to women (with the exception of family members, who are seemingly clueless about his condition), although he quickly learns that he is able to surpass this problem by consuming alcohol. Consequently, the alcohol makes him obnoxious. Raj has an interest a number of books and TV shows which are generally perceived as feminine, and targeted towards the female demographic, such as The Good Wife and Bridget Jones's Diary.

Family
Raj always communicates with his parents, Dr. V.M and Mrs. Koothrappali back in India via webcam. Not much of Raj's family is explored so far. A running gag in the series is that Raj claims that he grew up in poverty, which he likes to say to people to womanize and make him interesting and mystical, only for his friends to remind him that Raj comes from a wealthy background, his Father is a gynaecologist, drives a Bentley and he has a house full of servants; two of them children. Raj later admits this, saying they are very wealthy. His parent say this too, believing they have nothing to complain about as they are rich in a poor country. Raj as a matter of fact comes from a very large family; He comes from a family of six children, according to The Hot Troll Deviation.

Raj's cousin, Sanjay Koothrappali (or, as he says his friends know him as "Dave from AT&T Customer Service"), works in a Call Centre, and is briefly mentioned in various episodes. In The Guitarist Amplification, Raj tried to circumvent going to his wedding, but eventually accepted his parents' offer.

Another cousin, Venkatesh (who appeared in The Precious Fragmentation ), works as a lawyer in Mumbai. Albeit, he has poor negotiation skills, who even admits that he is useless.

Raj is also mentioned to have an older brother in one episode, who, according to Raj, painted and gave him his 'Patang' (fighter kite), but this was eventually surrendered to Sheldon in a game of kite fighting, thanks to Howard. However, his older brother appears to be one Raj's three brothers, according to his statement in The Hot Troll Deviation. It was in this episode where Raj claimed that he has two sisters, one of them Priya.

In The Alien Parasite Hypothesis, Raj mentions that Type 2 diabetes runs in his family but he has no symptoms so far.

Leonard Hofstadter
The bond that Leonard and Raj share has never been very profound with them being only moderately close, they meet at the University in The Staircase Implementation.

Sheldon Cooper
Raj has an admirable toleration towards Sheldon's insufferable attitude, although this maybe because of religious reasons. In the episode The Pirate Solution, when Raj's research hit a dead end, Sheldon offered Raj a chance to work for him, which he later accepted. Since then Raj has been working for Sheldon.

Howard Wolowitz
Howard is Raj's best friend, since the first season they have always been very close. Although Raj and Howard are heterosexual, their relationship and interaction sometimes resembles that of a couple, which resulted in a misunderstanding by Leonard's Mother, who called their relationship as an "ersatz homosexual marriage".

Penny
Penny is the closest female friend that Raj has, though he is only able to talk to her when he is drunk. There are times where his relationship with Penny becomes less than platonic - particularly in the episode The Griffin Equivalency where, misinterpreting her going with him to an award ceremony as an act of romance rather than friendship, he introduced Penny to his parents as his new "squeeze" while he was drunk. He tried to apologize by note but Penny forced him to say the apology while sober. In the last episode of the season 4 finale, Raj and Penny hooked up while they were drunk in Leonard's bedroom, and when they were leaving the bedroom, ran into Howard, Leonard and Sheldon. Raj wasn't able to talk to Penny even after they slept together.

Romantic
Unlike the other main characters, Raj's romantic relationships have never been very serious or lasting. He has had a number of one-night-stands and brief dates. Impressively though, Raj was the first one amongst the four to get laid within the series in The Middle Earth Paradigm, at Penny's Halloween party.

Dr. Elizabeth Plimpton (Judy Greer)
Dr. Plimpton was welcomed as a guest of Sheldon's for a few days while considering taking a position at the University. Incredibly promiscuous, she shows interest in Raj immediately after meeting him despite having slept with Leonard the previous night and sitting next to him at the time. That evening, Raj was hosting Dr. Plimpton but when Leonard and Howard show up, she immediately suggests they join Raj and her. Raj tricks his friends into leaving and spends the night with Dr Plimpton.

Lalita Gupta (Sarayu Rao )
One of Raj's female childhood acquaintance, when they were young she used to be fat and bullied Raj. In spite of this, Raj's parents thought it would be a good idea to set them up on a date. In that episode Raj discovers that alcohol is able to help him suppress his selective mutism but being drunk made him obnoxious. As a result, he generally mistreated Lalita and Sheldon, mistaking her for a beloved childhood fairy tale character, unintentionally stole Lalita.

Missy Cooper (Courtney Henggeler)
In The Pork Chop Indeterminacy, Sheldon's fraternal twin sister, Missy, came to Pasadena. Raj, at the time was using an experimental drug to help with his selective mutism. Leonard, Howard and Raj were all attracted to her and after hitting on her too much (causing her to hide at Penny's for the night) and fighting over the "right" to ask her out, they decide to just ask her out individually.. After both Leonard and Howard's attempts failed, Raj got his turn. Inconveniently, as he waited for her at Penny's door, the drugs began wearing off and despite Missy's implied interest in Raj, (saying "Hi cutie pie, I was hoping you'd show up") Raj was unable to ask her out and had.

Abby (Danica McKellar )
In the episode The Psychic Vortex, Leonard and Howard went on a double date with their respective girlfriends, leaving a lonely Raj with only an indifferent Sheldon. Raj insists on Sheldon helping him score with a girl at a University Mixer. After presenting Sheldon with a "Limited Edition Green Lantern Lantern" and a "Incredible Hulk Hands signed by Stan Lee" on two separate occasions, Sheldon agreed to be Raj's wingman, helping him score with Abby. It is not known what happened to her after that episode.

Trivia

 * He is 30 years old. He was born on October 6 1981.
 * He has a Ph.D from astrophyics.
 * Raj is completely not at all serious about his Hindu faith, and eats beef, which is considered a sin.
 * Raj, much like Howard, despises much of Sheldon's antics, and the two managed to get Sheldon on a date with Amy Farrah Fowler on a dating website in The Lunar Excitation, much to Sheldon's dismay.
 * Raj's case of selective mutism was evident in the Pilot episode.
 * "Koothrappali" is a surname from southern India; however Raj claims that he is from Delhi, suggesting that his family moved from their native area.
 * Whenever Raj gets an idea or wants to say something slightly controversial in a conversation, he whispers it in Wolowitz's ear whenever a woman is around. Wolowitz never wants to say it out loud because it finds it stupid or offensive, but he ends up saying it anyway through scoffing Raj. Sheldon hates him talking in his ear altogether, although he does appreciate Raj's words.
 * He regularly communicates with his parents (V. M. Koothrappali and Mrs. Koothrappali) back in India via webcam. When they become meddling or judgmental, he often "brings his parents" into Leonard and Sheldon's apartment via his MacBook Pro, to seek his friends' support in the discussion.
 * His father is a gynecologist and drives a Bentley.
 * Rajesh often has married-couple-like arguments with Wolowitz and, when nervous, often whispers into his ear leaving him to translate to everyone else.
 * As with Wolowitz, the others in his circle of friends often refer to him by his surname. He frequently wears a purple jacket and a sweater vest.
 * Rajesh performs vocals when playing Rock Band (albeit extremely badly), which could possibly be a joke because he suffers from selective mutism. Though in a Season 2 promotional photo, he is playing with a guitar controller, so he is either playing the bass or the lead.
 * He despises Guitar Hero because he feels it is lame, though he still plays it.
 * Raj is considered the attractive one of the group because women find him foreign and exotic, plus his selective mutism makes him a very 'good listener'.
 * Works with/for Sheldon.
 * Featured in People Magazine (30 Under 30 to Watch!)
 * He has MySpace.
 * He has problems talking to women unless he is drunk. In one episode he had special medication for his problem, but stopped taking it due to the side effects.
 * Unlike the other guys, Raj has shown great interest in some non-geeky and sometimes feminine things, such as Grey's Anatomy, The Good Wife, Sex and the City, Eat Pray Love, Bridget Jones' Diary and John Grisham novels. He also likes Archie comics along with Zack and likes Twilight.
 * Raj, as a matter of fact, is addicted to internet pornography.
 * Raj often obsesses over almost-insignificant details in fiction, such as how toilets in Atlantis in Aquaman work, the possible symbolism of ponytails in Avatar, whether Wolverine's prostate is made of adamantium, what zombies would eat if humanity was exterminated, how vampires would shave themselves if they can't see their reflections, etc.
 * English is his native language, though he speaks very fluent Hindi.
 * Raj doesn't need to be drunk to talk to woman, as long as he thinks he is drunk it is sufficient (Placebo Effect ) as shown in "The Terminator Decoupling".
 * Raj takes pilates classes and claims to, as a result, have very well-trained abs.
 * In one scene when parents arranged a blind date he refused and Sheldon explains that Indian arranged marriages result in a peaceful bonfd then Raj says "I know my own culture" leaving Sheldon quite silenced.
 * In one episode Sheldon will join Penny in jogging and Howard says to Penny Raj always watches you from his car with binoculars.
 * Like the common nerd, Raj was bullied as a child, although he was unique as he once got a penis drawn on his forehead on his first day of cricket camp, with the testicles drawn around the eyes. One person who bullied him was Lalita Gupta, who used to kick him in the shins and call him untouchable. They dated as adults, where a drunk Raj insults her by saying she used to be so, so fat as a child.
 * His favorite number is 5,318,008. The reason for that is that when entered in a calculator, turning the calculator upside-down will read "Boobies".
 * Raj is terrified of bugs. As he is also afraid of women, Sheldon jokes that Ladybugs must render him cationic.
 * He was mad when Leonard and Priya decided to date again which means he is careful towards his baby sister.
 * In The Roommate Transmogrification, Raj had a drunken sexual encounter with Penny, which they both apparently regretted instantly.
 * Though it is claimed that Raj can only talk to Penny when he is drunk, in an episode in Season 4, he is able to talk to Penny during lunch with Priya and the guys in the Cheesecake Factory.