Bert asks for Sheldon's help in a geology research project relating to dark matter. Sheldon secretly agrees, but is too embarrassed to admit he is working with rocks. Bert finds out about this and ends their partnership. After talking with Amy, Sheldon goes to apologize, only to find Leonard has taken his place. Meanwhile, Raj runs into Ruchi again and goes out with her, but she does not believe in romantic love. After Howard and Bernadette tell Raj that he can just have sex with Ruchi, he agrees to keep it casual.
The men are excited that Bill Gates is visiting Penny's pharmaceutical company, although she says that she cannot bring them along. Sheldon believes that it's an April Fools' Day prank. Leonard sees what hotel Gates is staying at on Penny's schedule, so he, Raj and Howard meet him in the lobby the day before. Once Sheldon sees proof, the men twice send him to the wrong hotel as real pranks. Penny says Leonard can meet Gates for real, so he fakes being sick to avoid him. When Penny puts Gates on a video call, he recognizes Leonard from the previous night. Meanwhile, Amy is tired of Bernadette only talking about her children, so Bernadette uses her expanded parental brain to learn random science facts.

Through the use of his vanity cards at the end of episodes, Lorre alleged that the program had been plagiarized by a show produced and aired in Belarus. Officially titled Теоретики (The Theorists), the show features "clones" of the main characters, a similar opening sequence, and what appears to be a very close Russian translation of the scripts.[207] Lorre expressed annoyance and described his inquiry with the Warner Bros. legal department about options. The television production company and station's close relationship with the Belarus government was cited as the reason that any attempt to claim copyright infringement would be in vain because the company copying the episodes is operated by the government.[208]
Laura Spencer as Emily Sweeney (recurring seasons 7–8, 10, starring season 9):[55] A dermatologist at Huntington Hospital. Emily went to Harvard and delights in the macabre and states that she likes her job because she can cut things with knives. Prior to meeting Raj, Emily was set up on a blind date with Howard. After finding Emily's online dating profile, Raj has Amy contact her as his wingman instead. Their relationship becomes exclusive, but Raj later breaks up with Emily when he becomes infatuated with the bartender Claire (Alessandra Torresani).
By season seven, Galecki, Parsons, and Cuoco were also receiving 0.25% of the series' back-end money. Before production began on the eighth season, the three plus Helberg and Nayyar, looked to renegotiate new contracts, with Galecki, Parsons, and Cuoco seeking around $1 million per episode, as well as more back-end money.[36] Contracts were signed in the beginning of August 2014, giving the three principal actors an estimated $1 million per episode for three years, with the possibility to extend for a fourth year. The deals also include larger pieces of the show, signing bonuses, production deals, and advances towards the back-end.[37] Helberg and Nayyar were also able to renegotiate their contracts, giving them a per-episode pay in the "mid-six-figure range", up from around $100,000 per episode they each received in years prior. The duo, who were looking to have salary parity with Parsons, Galecki, and Cuoco, signed their contracts after the studio and producers threatened to write the characters out of the series if a deal could not be reached before the start of production on season eight.[38] By season 10, Helberg and Nayyar reached the $1 million per episode parity with Parsons, Galecki, and Cuoco, due to a clause in their deals signed in 2014.[39]
Wil Wheaton brings William Shatner on his Professor Proton show to meet Sheldon, who gets so excited that he vomits on Shatner. Going to Wil to apologize, he finds Wil hosts a Dungeons & Dragons group with his celebrity friends including Shatner. Finding out Stuart is in the group and never told them, the guys make Stuart panic and quit. Wil secretly invites Leonard who discovers that the group also includes Shatner, Kevin Smith, Joe Manganiello and Kareem Abdul-Jabbar. Leonard tells Penny, who tells Amy and Bernadette, all three women having a crush on Manganiello. Because of that indiscretion, Wil kicks out Leonard and admonishes the guys for using him for his connections, and says that one of the worst things about being a celebrity is not knowing whether someone will like him for himself. To apologize, the guys invite Wil to play D&D with them at Leonard’s apartment, but Wil, secretly in the middle of a game with Penny, Amy and Bernadette and the group, politely turns them down, before allowing the girls to send them a photo of the events as payback.
Bernadette's due date arrives but she still hasn't given birth. As Amy and Howard work together at the college, the rest of the friends try various ways to initiate her labor, though Sheldon wants to play a complicated board game instead. Amy shocks Howard by saying Bernadette has already decided to name the baby after her father, Michael. He doesn't agree and everyone makes suggestions as to what to name the baby. Bernadette goes into labor and gives birth to a son named Neil, after Neil Armstrong, Neil Gaiman, and Neil Diamond, with Michael as the middle name. At the last minute, Howard relents to name him Michael as Bernadette got six stitches.
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.[4][5] 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.
In the season eight finale, Sheldon and Amy get into a fight about commitment on their fifth anniversary. Amy tells Sheldon that she needs to think about the future of their relationship, unaware that Sheldon was about to propose to her. Season nine sees Sheldon harassing Amy about making up her mind until she breaks up with him. Both struggle with singlehood and trying to be friends for the next few weeks until they reunite in episode ten and have sex for the first time on Amy's birthday.

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.
Bert asks for Sheldon's help in a geology research project relating to dark matter. Sheldon secretly agrees, but is too embarrassed to admit he is working with rocks. Bert finds out about this and ends their partnership. After talking with Amy, Sheldon goes to apologize, only to find Leonard has taken his place. Meanwhile, Raj runs into Ruchi again and goes out with her, but she does not believe in romantic love. After Howard and Bernadette tell Raj that he can just have sex with Ruchi, he agrees to keep it casual.

When Bernadette tells Howard that she is expecting again, he is once again floored with fear about raising another child, particularly when he learns it’s a boy. Howard, who isn't athletically inclined, worries he will not be able to relate to a son who might one day expect his dad to be the stereotypical father. Despite his best attempts to get out of it, Howard has a vasectomy to avoid any future surprises and is placed on bed rest, joining his pregnant wife at home.
Keith Carradine has appeared in three episode as Penny's father, Wyatt, first in Season 4. Katey Sagal, who played the on-screen mother of Kaley Cuoco's character in the 2002-2005 sitcom 8 Simple Rules, has appeared as Penny's mother in one episode of The Big Bang Theory. Jack McBrayer has appeared in one episode of The Big Bang Theory as Penny's brother, Randall.
The CBS sitcom said goodbye on Thursday night after a storied 12-season run — and now that it’s really over, we’re feeling super nostalgic. Having already revisited the pilot episode, highlighted classic “Shamy” moments and ranked our favorite recurring characters, we’re closing out our retrospective coverage with a list of the 10 episodes that we feel are a cut above the rest.
Through the use of his vanity cards at the end of episodes, Lorre alleged that the program had been plagiarized by a show produced and aired in Belarus. Officially titled Теоретики (The Theorists), the show features "clones" of the main characters, a similar opening sequence, and what appears to be a very close Russian translation of the scripts.[207] Lorre expressed annoyance and described his inquiry with the Warner Bros. legal department about options. The television production company and station's close relationship with the Belarus government was cited as the reason that any attempt to claim copyright infringement would be in vain because the company copying the episodes is operated by the government.[208]
Kunal Nayyar has the flick Think Like a Dog in post-production and the upcoming Trolls World Tour in pre-production. Nayyar provides the voice of Guy Diamond in the movie series. Aside from that, however, the former Raj Koothrappali is looking forward to some much needed family time. "I'm going to go to India, spend more time with my parents," he told Parade in late April. "I left my country when I was 18, so it's important for me to go home and spend time with mom and dad, so that's the main focus right now.
The Canadian alternative rock band Barenaked Ladies wrote and recorded the show's theme song, which describes the history and formation of the universe and the Earth. Co-lead singer Ed Robertson was asked by Lorre and Prady to write a theme song for the show after the producers attended one of the band's concerts in Los Angeles. By coincidence, Robertson had recently read Simon Singh's book Big Bang,[25][26] and at the concert improvised a freestyle rap about the origins of the universe.[citation needed] Lorre and Prady phoned him shortly thereafter and asked him to write the theme song. Having been asked to write songs for other films and shows, but ending up being rejected because producers favored songs by other artists, Robertson agreed to write the theme only after learning that Lorre and Prady had not asked anyone else.[citation needed]

The sixth season boasts some of the highest-rated episodes for the show so far, with a then-new series high set with "The Bakersfield Expedition", with 20 million viewers,[97] a first for the series, which along with NCIS, made CBS the first network to have two scripted series reach that large an audience in the same week since 2007. In the sixth season, the show became the highest rated and viewed scripted show in the 18–49 demographic, trailing only the live regular NBC Sunday Night Football coverage,[98][99] and was third in total viewers, trailing NCIS and Sunday Night Football.[100] Season seven of the series opened strong, continuing the success gained in season six, with the second episode of the premiere, "The Deception Verification", setting the new series high in viewers with 20.44 million.[101][102]
When Raj misses out on a job at the planetarium, his father says he has no confidence because Howard always makes fun of him. Raj distances himself from Howard and later gets the job. Howard is hurt by this (even after apologizing to him) and tries to make amends with Raj after his first performance at the planetarium but, when he sees him get a date, he leaves without speaking to him, thinking that the latter's life is better without him. Meanwhile, Sheldon and Amy try randomly dividing up wedding tasks, but they keep arguing. The only thing they can agree on is to get married, so they decide to just get married at City Hall. However, Sheldon decides that he wants a first dance with his new wife and they go home to plan their wedding.
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