The American television sitcom franchise The Big Bang Theory, began with the multi-cam laugh track sitcom of the same name created and executive produced by Chuck Lorre and Bill Prady, which premiered on CBS on September 24, 2007, and ended on May 16, 2019, followed by the single-camera spin-off prequel television series Young Sheldon, created and executive produced by Lorre alongside Jim Parsons and Steven Molaro, which premiered on CBS on September 25, 2017 and concluded on May 16, 2024, with the third series in the franchise, a multi-cam spin-off sequel to Young Sheldon entitled Georgie & Mandy's First Marriage, premiering on October 17, 2024. A fourth series, a multi-cam spin-off sequel to The Big Bang Theory entitled Stuart, Denise & Bert, is slated to premiere in 2025.
The Big Bang Theory initially centers on five characters: Sheldon Lee Cooper and Leonard Hofstadter, two physicists and roommates; Penny, their neighbor who is a waitress and aspiring actress; Sheldon and Leonard'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.