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. 

Howard dresses as Sheldon for Halloween at work, hurting Sheldon's feelings. When Howard does not apologize, Amy and Sheldon dress as Bernadette and Howard at Penny and Leonard's party, angering Bernadette. Sheldon and Bernadette later bond over their painful childhood memories. Leonard is upset that Penny does not seem to remember that their first kiss was on Halloween. Penny later admits she does remember, but does not like to think of their first kiss as an unromantic drunken hookup. She likes to imagine their first kiss was one they shared on Leonard's birthday, which pleases him.
David Saltzberg, a professor of physics and astronomy at the University of California, Los Angeles, checks scripts and provides dialogue, mathematics equations, and diagrams used as props.[4] According to executive producer/co-creator Bill Prady, "We're working on giving Sheldon an actual problem that he's going to be working on throughout the [first] season so there's actual progress to the boards ... . We worked hard to get all the science right."[5] David Saltzberg, who has a Ph.D. in physics, has served as the science consultant for the show for six seasons and attends every taping.[23] He sees early versions of scripts which need scientific information added to them, and he also points out where the writers, despite their knowledge of science, have made a mistake. He is usually not needed during a taping unless a lot of science, and especially the whiteboard, is involved.[24]
Initial reception for the series was mixed. The review aggregation website Rotten Tomatoes reported a 52% approval rating for the first season based on reviews from 23 critics, with an average rating of 5.18/10. The website's critical consensus reads, "The Big Bang Theory brings a new class of character to mainstream television, but much of the comedy feels formulaic and stiff."[91] On Metacritic, the season holds a score of 57 out of 100, based on reviews from 23 critics, indicating "mixed or average reviews".[92] Later seasons received more acclaim and in 2013, TV Guide ranked the series #52 on its list of the 60 Best Series of All Time.[93]
^ "Editor's Note: With final Monday ratings in, The Big Bang Theory has now reached a new series high in viewers (16.32m) and was the night's top program in adults 18-49 (5.9/15), up a tenth from this morning. -- "Two and a Half Men" Soars to Its Best Adult 18-49 Rating in Three Years". CBS. March 9, 2010. Archived from the original on January 8, 2014. Retrieved January 5, 2013.
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.
Leonard and Sheldon are brilliant physicists—geniuses in the laboratory but socially challenged everywhere else. Enter beautiful, street-smart neighbor Penny, who aims to teach them a thing or two about life. Despite their on-again, off-again relationship in the past, Leonard and Penny have finally gotten married. Even Sheldon has found a female companion, entering into a "relationship agreement" with neurobiologist Amy Farrah Fowler, and he recently took their relationship to the next level by marrying her after a long courtship. In their free time, Leonard and Sheldon enjoy fantasy role-playing games with their ever-expanding universe of friends, including fellow scientists Koothrappali, Wolowitz, and Wolowitz’s adorable microbiologist wife, Bernadette, who is adjusting to life with their two children.
The fourth season's second half began on June 30, 2011. Season 5 began airing on November 3, 2011, at 8:00 p.m. as part of E4's Comedy Thursdays, acting as a lead-in to the channel's newest comedy, Perfect Couples. Episode 19, the highest-viewed episode of the season, attracted 1.4 million viewers.[145] Season 6 premiered on November 15, 2012, with 1.89 million viewers and a further 469,000 on the time shift channel, bringing the total to 2.31 million, E4's highest viewing ratings of 2012, and the highest the channel had received since June 2011. The sixth season returned in mid-2013 to finish airing the remaining episodes.[146] Season 7 premiered on E4 on October 31, 2013 at 8:30pm and hit multiple ratings records this season. The second half of season seven aired in mid 2014.[147] The eighth season premiered on E4 on October 23, 2014 at 8:30 p.m.[148] During its eighth season, The Big Bang Theory shared its 8:30 p.m. time period with fellow CBS comedy, 2 Broke Girls. Following the airing of the first eight episodes of that show's fourth season, The Big Bang Theory returned to finish airing its eighth season on March 19, 2015.[149]

When Leonard receives a braggy Christmas letter from his brother, he feels bad about how little he and Penny have achieved in the past year. Leonard wonders if he and Penny should be thinking about the next step after two years of marriage, like buying a house or having a baby. Penny tells him she wants to do all those things someday, but she has a bunch of stuff she would like to do first.
He's since become attached to a handful of Netflix projects, appearing in their recent Ted Bundy film Extremely Wicked, Shockingly Evil and Vile, executive producing mentee Ryan O'Connell's autobiographical comedy series Special, and signing on to reprise his role in their movie version of Ryan Murphy's Broadway production of The Boys in the Band, due on the streaming service in 2020.
Kaley Cuoco as Penny:[44] An aspiring actress from Omaha, Nebraska. Penny moves in across the hall from Sheldon and Leonard. She waits tables 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.
When Amy sees Sheldon obsessively tying and untying his bow tie the day before their wedding, Amy tells him it doesn't need to be even because sometimes a little asymmetry looks good. On the day of the wedding, Sheldon stops his mother from trying to straighten his bow tie, saying it's supposed to be a little asymmetrical. When Mary comments that sometimes it’s the imperfect stuff that makes things perfect, Sheldon has a flash of inspiration and rushes to see Amy. Sheldon and Amy’s wedding is delayed as they excitedly work on a new theory of “super asymmetry”.
Filming proceeds smoothly – makeup artists do touch-ups, a prop master replenishes the pickle supply – with humor and camaraderie between takes. When a reshoot is needed because Simon Helberg, who plays Howard, held his napkin in the wrong hand, Kaley Cuoco, who plays Penny, lifts her food box high and mockingly asks, “Does it go over my head? I don’t remember.”
Initial reception for the series was mixed. The review aggregation website Rotten Tomatoes reported a 52% approval rating for the first season based on reviews from 23 critics, with an average rating of 5.18/10. The website's critical consensus reads, "The Big Bang Theory brings a new class of character to mainstream television, but much of the comedy feels formulaic and stiff."[91] On Metacritic, the season holds a score of 57 out of 100, based on reviews from 23 critics, indicating "mixed or average reviews".[92] Later seasons received more acclaim and in 2013, TV Guide ranked the series #52 on its list of the 60 Best Series of All Time.[93]
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.
And while the actor, 44, doesn't have any other gigs lined up just yet—his most recent stab at producing, CBS' Living Biblically, was canceled after 13 episodes in 2018—he's busy preparing for his biggest role yet: fatherhood. On May 3, 2019, he and girlfriend Alaina Meyer announced that they were expecting their first child together. "We are absolutely over the moon to announce that we will soon be welcoming a little one into this crazy and wonderful world," he wrote on social media, sharing the big news. "There truly is love out there for all. We hope ours is the ember of yours, as we feel yours is the ember of ours."
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.

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 Young and the Restless Spoilers: Nikki Can’t Stop Victor’s Custody Fight – Sharon’s Vengeful Fury Exposes Cover-Up Crew General Hospital Spoilers: Elizabeth Hendrickson Hints at Fan Favorite Destruction and Supercouple Breakup Shockers The Bold and the Beautiful Spoilers: Thorne and Katie Use Bill’s Secret Weapon Against Him – Shocking Scheme from New B&B Couple
^ "Editor's Note: With final Monday ratings in, The Big Bang Theory has now reached a new series high in viewers (16.32m) and was the night's top program in adults 18-49 (5.9/15), up a tenth from this morning. -- "Two and a Half Men" Soars to Its Best Adult 18-49 Rating in Three Years". CBS. March 9, 2010. Archived from the original on January 8, 2014. Retrieved January 5, 2013.
Two months after the events of "The Change Constant", Sheldon and Leonard repair Sheldon's DNA molecule model as everyone prepares to fly to Sweden for the Nobel Prize award ceremony. Howard and Bernadette nervously leave their kids for the first time with Stuart and Denise, while Raj leaves his dog with Bert. Penny has become pregnant, though she and Leonard are keeping it a secret. On the flight, Raj thinks he spots Sarah Michelle Gellar. Penny's frequent bathroom trips make Sheldon fear she is sick. Leonard reveals the pregnancy to Sheldon, but instead of being excited for Penny, Sheldon is only selfishly relieved that he will not get sick and he exposes the pregnancy, offending Leonard. At the hotel, a series of minor incidents with their kids make Howard and Bernadette want to go home. Much to their dismay, Sheldon is still insensitive. Amy furiously tells Sheldon he broke their friends' hearts and they only tolerate him because he does not intentionally do so, which she also sometimes does. Everyone decides to stay for the ceremony and Raj brings Gellar. After they are awarded their medals, Amy encourages girls to pursue science while Sheldon thanks his family and then individually acknowledges each of his friends and Amy as his other family who always support him. The episode closes with the gang eating in Apartment 4A (an allusion to the final scene in the opening credits) as an acoustic version of the theme song's chorus plays.
While opening their wedding gifts, Sheldon and Amy cannot figure out the purpose of the glass shard Leonard and Penny gave them. They decide it must be a clue to a scavenger hunt to the real gift. They eventually end up in the coffee shop where they first met and find a locket in the lost and found that they think must be the real gift. The glass shard was actually a crystal chakra wand that Raj gave as a gift to Howard and Bernadette, who then re-gifted it to Leonard and Penny, who finally passed it on as a joke. Leonard and Penny find it less funny when they are given a coded thank-you note they have to use to unlock their WiFi. After making out with his employee Denise at Sheldon and Amy's wedding reception, Stuart finally asks Denise out on a date; while preparing for the date, he has a spray-tan accident, but she just finds it funny and still goes out with him. Raj is depressed everyone else has a relationship and asks his father to arrange a marriage.
Raj meets with the woman his father set up for him, Anu. Her commanding personality and practical approach to marriage startle Raj but he agrees to go ahead with it. Howard criticizes him but apologizes; he just never expected Raj to give up on romance. Raj admits this to Anu so she proposes to him, and he says yes. Raj also sends out a relationship questionnaire to Leonard and Penny, which soon reveals that Penny does not think she ever wants kids, upsetting Leonard, who would like to have kids someday, and their friends selfishly badger them on the issue. After telling her father Wyatt who is also upset, Leonard tells Penny that he'll be okay with it, as he never thought he'd have her in his life. To get his mind off of it, Penny rents Leonard a Batmobile to drive in and have fun with for the day. Meanwhile, Stuart starts bringing home Denise at night, which is very uncomfortable for Howard and Bernadette. When they also try to have time to themselves, they wake up their kids.
Sheldon has been writing to the reclusive scientist Dr. Wolcott (Peter MacNicol) who invites Sheldon to visit him in his completely isolated mountain cabin. The women quickly ask Leonard, Raj and Howard to tag along with him, making this his bachelor party, despite Sheldon's assertions that it shouldn't be called such. Wolcott has a brilliant mind but his behavior is very strange to the guys. He tells Sheldon he cut off all contact with others to focus on science. Though Sheldon enjoys the science, he decides that he doesn't want to live like Wolcott because of his friends and Amy. The guys leave to avoid Wolcott, whose theories about time make him doubt whether the guys were ever there. Meanwhile, Penny and Bernadette throw Amy a quilting bee for her bachelorette party, which she quickly finds boring. When Amy tells them she wants a night full of bad decisions as she earlier implied, they go to a bar where Amy drinks a few shots and passes out in twelve minutes. When she wakes up back at the apartment hungover and disappointed, the women lie and reassure her she had a wild time, involving her drunkenly riverdancing.
Filming proceeds smoothly – makeup artists do touch-ups, a prop master replenishes the pickle supply – with humor and camaraderie between takes. When a reshoot is needed because Simon Helberg, who plays Howard, held his napkin in the wrong hand, Kaley Cuoco, who plays Penny, lifts her food box high and mockingly asks, “Does it go over my head? I don’t remember.”
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]
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