Rajesh Ramayan "Raj" Koothrappali, Ph.D. (born October 6) is a fictional character on the CBS television series The Big Bang Theory, portrayed by actor Kunal Nayyar.
Rajesh is Howard Wolowitz's (Simon Helberg) best friend. He works as an astrophysicist in the Physics Department at Caltech. His principal characteristic is a case of selective mutism which does not allow him to talk to women outside of his family or while not under the influence of alcohol, or believing that he consumed alcohol.
Rajesh, who is normally called Raj or by his surname Koothrappali by Sheldon Cooper, is from New Delhi, India. However, he despises Indian food, and his knowledge regarding Indian culture and Hinduism is often disputed by Sheldon Cooper. He was born into a wealthy family and has five siblings, one of which is a previous girlfriend of Leonard, Priya. He is normally seen wearing a layered combination of a shirt and a vest, khakis, and a jacket. He wore a red cap only in the pilot episode.
All of the guys enjoy playing Halo every Wednesday at Sheldon and Leonard's apartment and occasionally at Koothrappali's apartment. They also play Age of Conan excessively, with Raj stating he has experienced gaming addiction.
In general terms, Raj is more patient with Sheldon than Leonard, Howard, or Penny; however Sheldon is oblivious to this as he once cut him off as a friend.
Raj has a "nervous bladder", meaning he gets an urge to relieve himself when under stress. This was shown when Penny got angry at him, and when he accompanied Leonard to confront Kurt over some money Kurt owed Penny.
One of Raj's primary personality quirks is his tendency to act or speak inappropriately according to the situation, especially when it is not called for, often earning him glares and negative remarks from the other characters. In the episode "The Love Car Displacement", when Leonard and Penny are about to have sex in a hotel room, he walked into the room and slept in the room, oblivious to what he had just interrupted. Later in that episode, when called by Sheldon to speak, he joins in the argument between Howard and Bernadette, though Sheldon had obviously hoped for him to salvage the conference's discussion about science.
Another recurring joke is how in his assimilation of American pop culture, Raj has developed a weakness for media that is more commonly consumed by females. Typically, one of the boys will slander the media in question (examples include Eat, Pray, Love, The Notebook, and Sex and the City) and Raj will eagerly put a word in to defend it, usually through an exasperated Howard, since it is normally Penny or Bernadette who brings up the topic. Their bickering only accentuates the homosexual undertones between him and Howard.
When hanging out with the guys, despite his particular Indian accent, Raj is noted for using slang ("fo' shizzle") and excessively using the word "dude". While he seems to speak fluent Hindi, his mother tongue is English