<Tr> <Td> </Td> <Td> This section describes a work or element of fiction in a primarily in - universe style . Please help rewrite it to explain the fiction more clearly and provide non-fictional perspective . (February 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> These actors are credited in all episodes of the series: </P> <Ul> <Li> Johnny Galecki as Leonard Hofstadter: An experimental physicist with an IQ of 173, who received his PhD when he was 24 years old . Leonard is a nerd who loves video games, comic books, and Dungeons & Dragons . Leonard is the straight man of the series, in which he shares an apartment in Pasadena, CA, with Sheldon . Leonard is smitten with his new neighbor Penny when they first meet, and they eventually marry . </Li> <Li> Jim Parsons as Sheldon Cooper: Originally from Galveston, Texas, Sheldon was a child prodigy with an eidetic memory who began college at the age of eleven, and earned a PhD at age sixteen . He is a theoretical physicist researching quantum mechanics and string theory, and despite his IQ of 187, he finds many routine aspects of social situations difficult to grasp . He is determined to have his own way, continually boasts of his intelligence, and has an extremely ritualized way of living . Despite these quirks, he begins a relationship with Amy Farrah Fowler, they are now engaged to marry . </Li> <Li> Kaley Cuoco as Penny: An aspiring actress from Omaha, Nebraska . Penny moves in across the hall from Sheldon and Leonard . She waits and occasionally tends the bar at the Cheesecake Factory . After giving up hope of becoming a successful actress, Penny becomes a pharmaceutical sales representative . Penny becomes friends with Bernadette and Amy, and they often hang out in each other's apartments . Penny and Leonard form a relationship and eventually marry . </Li> <Li> Simon Helberg as Howard Wolowitz: An aerospace engineer . Howard is Jewish and lives with his mother, Debbie (Carol Ann Susi). Unlike Sheldon, Leonard, Raj, Bernadette and Amy, Howard does not hold a doctorate . He goes into space, training as an astronaut and serving as a payload specialist . Howard initially fancies himself as a womanizer, but he later starts dating Bernadette, and they get engaged and married . Howard also has a tendency to waste money on toys and argues with Bernadette because of his oddly low income as an engineer and her high income as a pharmaceutical biochemist . </Li> <Li> Kunal Nayyar as Rajesh Koothrappali: A particle astrophysicist originally from New Delhi, India . Raj is initially unable to talk to women unless he drinks alcohol . Raj also has very feminine tastes and often takes on a stereotypical female role . Raj later dates Lucy (Kate Micucci), who also suffers from social anxiety, but it eventually ends; he later speaks to Penny without alcohol and thus overcomes his selective mutism . He begins dating Emily and their relationship later becomes exclusive . Raj also has a Yorkshire Terrier named Cinnamon . </Li> </Ul> <Li> Johnny Galecki as Leonard Hofstadter: An experimental physicist with an IQ of 173, who received his PhD when he was 24 years old . Leonard is a nerd who loves video games, comic books, and Dungeons & Dragons . Leonard is the straight man of the series, in which he shares an apartment in Pasadena, CA, with Sheldon . Leonard is smitten with his new neighbor Penny when they first meet, and they eventually marry . </Li>

The original cast of the big bang theory