The American television sitcom The Big Bang Theory, created and executive produced by Chuck Lorre and Bill Prady, premiered on CBS on September 24, 2007, while the American comedy spin-off prequel television series Young Sheldon, created and executive produced by Lorre alongside Jim Parsons and Steven Molaro, premiered on CBS on September 25, 2017.
The Big Bang Theory initially centers on five characters: Leonard Hofstadter and Sheldon Lee Cooper, two physicists and roommates; Penny, their neighbor who is a waitress and aspiring actress; and Leonard and Sheldon's friends and coworkers aerospace engineer Howard Joel Wolowitz and astrophysicist Raj Koothrappali.
Over time, several supporting characters have been introduced and promoted to starring roles, including physicist Leslie Winkle, neuroscientist Amy Farrah Fowler, microbiologist Bernadette Maryann Rostenkowski-Wolowitz, comic book store proprietor and friend of the other characters Stuart Bloom. The series also features numerous supporting characters, each of whom plays a prominent role in a story arc. Included among them are parents of the main characters, their dates and their coworkers. Celebrities such as Stephen Hawking appear in cameo roles as themselves.
Young Sheldon initially centers on Sheldon Cooper at the age of nine, going to high school and living with his family in the fictional town of Medford, East Texas, Sheldon's mother, Mary; his father and the head football coach at Medford High, George Sr.; his twin sister, Missy; his older brother, George Jr.; and his grandmother, Constance "Connie" Tucker, also known as "Meemaw". The series also features numerous supporting characters, each of whom plays a prominent role in a story arc. Included among them are Sheldon's present and former classmates, their dates and coworkers, and those of his family. Celebrities such as Elon Musk appear in cameo roles as themselves. Jim Parsons, who portrays the adult Sheldon Cooper on The Big Bang Theory, narrates the series and serves as an executive producer.
Main characters
Cast table
= Main cast (credited) = Recurring cast (2+ episodes) = Guest cast (1 episode)
The Big Bang Theory main characters
Leonard
Leonard Leakey Hofstadter (portrayed by Johnny Galecki; seasons 1-12) is an experimental physicist with an IQ of 173. Originally from New Jersey, he received his PhD at age 24, spending at least some of his time at Princeton University. He shared an apartment in Pasadena with colleague and friend Dr. Sheldon Cooper for much of the series. Unlike his equally geeky friends, Leonard is interested and adept in building relationships with other people. Compared to his friends, he is relatively successful with women. Leonard comes from an accomplished family. His mother, Dr. Beverly Hofstadter, is a neuroscientist and world-renowned psychiatrist with whom he has a strained relationship. His sister is a medical researcher, his father, Dr. Alfred Hofstadter, is an anthropologist, and his brother Michael is a Harvard law professor. He and Penny date on and off throughout the series, eventually marrying and finding out that Penny is pregnant in the series finale.
Leonard makes a brief non-speaking cameo as a child in the Season 2 finale of Young Sheldon; he was portrayed by Isaac Harger as a child.
Sheldon
Sheldon Lee Cooper (portrayed by Jim Parsons; seasons 1-12) is a theoretical physicist, possessing a B.S, M.S, M.A, Ph.D, Sc.D, I.Q. of 187, and eidetic memory. Born in East Texas, he was a child prodigy and received his PhD at age 16 from the California Institute of Technology. He is a cold, condescending, self-centered, and immature person but is rarely malicious. He is obsessed with routines and any disruptions distress him enormously. He shows signs of obsessive–compulsive personality disorder, often shown through his compulsive need to knock three times on a door while saying the name of the person behind the door 3 times too and the superiority complex. Despite his lack of social graces, he does care about his friends and family. In seasons 1–9, he shares an apartment in Pasadena with friend and fellow physicist Dr. Leonard Hofstadter. From then after, he moves in with his girlfriend and eventual wife, Amy. It is revealed in Young Sheldon that they have kids too.
His interest in science fiction and comic books borders on the extreme. He has a particular affinity for Spock from the Star Trek franchise. Although he has the tendency to take things literally, he is fond of occasionally telling a joke or playing a prank, which he typically punctuates with his trademark exclamation, "Bazinga!"