Well done! Really great final episode writing. The characters we have enjoyed for 12 seasons went on with their lives. . .but reached a happy place at that moment of time. Amy and Sheldon recognized for their brilliance. Penny and Leonard growing into a family. Bernadette and Howard being concerned about the children. Raj having someone fun to attend the ceremony with. Way to tie things up on a pleasant note.
As the theme of the show revolves around science, many distinguished and high-profile scientists have appeared as guest stars on the show. Famous astrophysicist and Nobel laureate George Smoot had a cameo appearance in the second season. Theoretical physicist Brian Greene appeared in the fourth season, as well as astrophysicist, science populizer, and physics outreach specialist Neil deGrasse Tyson, who also appeared in the twelfth season.
The show's pilot episode premiered on September 24, 2007. This was the second pilot produced for the show. A different pilot was produced for the 2006–07 television season but never aired. The structure of the original unaired pilot was substantially different from the series' current form. The only main characters retained in both pilots were Leonard (Johnny Galecki) and Sheldon (Jim Parsons), who are named after Sheldon Leonard, a longtime figure in episodic television as producer, director and actor. A minor character, Althea (Vernee Watson), appeared in the first scene of both pilots that was retained generally as-is. The first pilot included two female lead characters - Katie, "a street-hardened, tough-as-nails woman with a vulnerable interior" (played by Canadian actress Amanda Walsh) and Gilda, a scientist colleague and friend of the male characters (played by Iris Bahr). Sheldon and Leonard meet Katie after she breaks up with a boyfriend and they invite her to share their apartment. Gilda is threatened by Katie's presence. Test audiences reacted negatively to Katie, but they liked Sheldon and Leonard. The original pilot used Thomas Dolby's hit "She Blinded Me with Science" as its theme song.
On March 13, 2017, CBS ordered the spin-off Young Sheldon series. Jon Favreau directed and executive produced the pilot. Created by Lorre and Molaro, the series follows 9-year-old Sheldon Cooper as he attends high school in East Texas. Alongside Armitage as 9-year-old Sheldon Cooper and Perry as Mary Cooper, Lance Barber stars as George Cooper, Sheldon's father; Raegan Revord stars as Missy Cooper, Sheldon's twin sister; and Montana Jordan as George Cooper Jr., Sheldon's older brother. Jim Parsons reprises his role as adult Sheldon Cooper, as narrator for the series. Parsons, Lorre, Molaro and Todd Spiewak will also serve as executive producers on the series, for Chuck Lorre Productions, Inc. in association with Warner Bros. Television. The show's pilot episode premiered on September 25, 2017. Subsequent weekly episodes began airing on November 2, 2017 following the broadcast of the 237th episode of The Big Bang Theory.
The show originally centered on five characters living in Pasadena, California: Leonard Hofstadter and Sheldon Cooper, both physicists at Caltech, who share an apartment; Penny, a waitress and aspiring actress who lives across the hall; and Leonard and Sheldon's similarly geeky and socially awkward friends and co-workers, aerospace engineer Howard Wolowitz and astrophysicist Raj Koothrappali. Over time, supporting characters were promoted to starring roles, including neuroscientist Amy Farrah Fowler, microbiologist Bernadette Rostenkowski, physicist Leslie Winkle and comic book store owner Stuart Bloom.
Professor Proton, Sheldon's favorite childhood show, is being rebooted. After unsuccessfully auditioning for the part, he goes to Wil Wheaton for acting tips for his second audition. However, Sheldon is later dismayed when Wil is offered the role instead. Talking it over with Arthur in his dreams, he is still upset to see his idol replaced and considers Wil an enemy again. Meanwhile, Howard gets a vasectomy while Bernadette is on bed rest. Penny offers to take care of Halley for them, but they insult her by expecting her to be irresponsible. Halley ends up saying her first word by calling Penny "Mama."
Science has also interfered with the characters' romantic lives. Leslie breaks up with Leonard when he sides with Sheldon in his support for string theory rather than loop quantum gravity. When Leonard joins Sheldon, Raj, and Howard on a three-month Arctic research trip, it separates Leonard and Penny at a time when their relationship is budding. When Bernadette takes an interest in Leonard's work, it makes both Penny and Howard envious and results in Howard confronting Leonard, and Penny asking Sheldon to teach her physics. Sheldon and Amy also briefly end their relationship after an argument over which of their fields is superior.
Leonard Hofstadter and Sheldon Cooper are both brilliant physicists working at Cal Tech in Pasadena, California. They are colleagues, best friends, and roommates, although in all capacities their relationship is always tested primarily by Sheldon's regimented, deeply eccentric, and non-conventional ways. They are also friends with their Cal Tech colleagues mechanical engineer Howard Wolowitz and astrophysicist Rajesh Koothrappali. The foursome spend their time working on their individual work projects, playing video games, watching science-fiction movies, or reading comic books. As they are self-professed nerds, all have little or no luck with women. When Penny, a pretty woman and an aspiring actress from Omaha, moves into the apartment across the hall from Leonard and Sheldon's, Leonard has another aspiration in life, namely to get Penny to be his girlfriend. Written by Huggo
Sheldon is still despondent over the disproving of his and Amy's theory on asymmetry. Leonard brings out a VHS tape of a pep talk that Sheldon recorded as a boy, but it turns out that his father had recorded a long-ago football game over it. Sheldon, however, is buoyed by a halftime pep talk his father gave the team, realizing he and his father had more in common than he previously thought. This causes Amy to view asymmetry and symmetry in another manner and they decide their theory may not be dead after all. Bernadette finds an old tape of Howard preparing to audition for The Magic Castle. She insists he fulfill his dream and audition with her as a coach, drawing on her beauty pageant experience. Howard eventually decides to audition his own way, and promptly botches his chances by accidentally destroying a judge's Rolex.
Sheldon is annoyed that Amy does not have time to work on the super-asymmetry project with him so he talks President Siebert into getting her removed from her own project at the university. Amy is angry at both of them as she wants to still have her own identity outside the marriage. When confronted by Amy, Siebert apologizes to her but states that it will be difficult for the university to give her her project back. After talking with Arthur Jeffries in a dream, Sheldon apologizes to Amy and both of them talk about their fears in their marriage. Meanwhile, Raj does not want to have Howard join him in his show at the planetarium, thinking he'd just use his astronaut status to make it about himself. Raj eventually lets him join in and Raj and Howard spend the whole time complimenting each other, surprising Bernadette, Leonard and Penny.
Sheldon and Amy decide on a wedding date of May 12th. They want to have their reception at the Athenaeum at Caltech. While scouting the location, they are shocked to see Leonard and Penny eating there, as Leonard had told Sheldon their application had been denied. In reality, Leonard just wanted a place to avoid Sheldon. Kripke has booked the venue for his birthday party on the same day as the wedding. Leonard cleans radioactive sludge for Kripke to get the date for Sheldon as an apology for lying. Kripke eventually agrees to change the day but when Amy hears he wants to sing at the wedding, she suggests they get married at the Griffith Observatory instead. Meanwhile, Bernadette and Howard are unsure if one of them should quit their job to stay home with the children. Howard volunteers, but when left alone with the children he passes out exhausted, leaving Raj in charge. When Bernadette meets Penny for lunch, she realizes that she loves being at the office again, but doesn't want to leave the children. She and Howard promise to figure it out later after they take a nap.
Amy and Howard begin collaborating on a neuroprosthetics project, upsetting Sheldon and Raj, who feel they are not spending as much time with them. When they seek solace with an annoyed Bernadette, she exploits the situation to trick Sheldon into doing Howard's chores. Penny successfully employs the approaches recommended in one of Bernadette's parenting books to deal with Sheldon, but Leonard believes she is coddling Sheldon too much. Sheldon and Raj resolve the issue of missing their significant others by spending time together.