Raj moves in with Leonard and Penny and a period of adjustment begins for the three, while the usually self-centered Sheldon shows surprising interest in Amy's work.
When Raj moves out of his apartment to save money, both Howard and Bernadette and Leonard and Penny offer him a place to stay. Meanwhile, Sheldon calls Leonard's mother for relationship advice.
When Raj no longer receives money from his father, he asks Sheldon to help him manage his finances. Meanwhile, Penny insists on joining Leonard at Comic-Con and Bernadette finally figures out a way to get Howard to do some of the housework.moreless
Amy is incensed when she discovers Sheldon has shared intimate relationship information with people at the university; and Raj is knocked for a loop when his father stops sending financial support.
When Sheldon hinders progress on the guidance-system project, Leonard comes up with a plan to get rid of him by giving him tickets to a historic railroad. Meanwhile, Penny and Amy take new-mommy Bernadette on a girls' night out, leaving baby Halley in the hands of Raj and Stuart.moreless
Sheldon is intrigued with the of beta testing an MIT designed machine that purports to help read people’s emotions. Leonard tries to hide his anger when Penny announces that her brother is coming to town and staying with them and Raj invites his ex-girlfriends to give him dating advice.moreless
The gang talks about what they did over the holidays. Sheldon and Amy go to visit Sheldon's mom, who is thrilled that they are living together, which confuses Sheldon. Leonard and Penny go through a hard time getting their Christmas tree and Howard and Bernadette have a hard time getting their baby to stop crying.moreless
The time comes for Howard and Bernadette to have their baby and the gang all wait together at the hospital. Meanwhile, it is Amy's birthday and she and Sheldon plan on having their annual night of romance.moreless
Sheldon and Leonard fight when it comes to dividing up their joint possessions while Raj and Stewart trip over themselves in helping Bernadette during the final weeks of her pregnancy.
A geologist coworker's MacArthur Genius fellowship award leaves Sheldon stone cold jealous. Meanwhile, Howard stumbles upon a remote-control Stephen Hawking action figure that he invented. Hawking appears as himself.
A successful gene experimentation leaves Sheldon excited to procreate with Amy, and he pulls out all stops to get her on board. Meanwhile, Raj is reluctant to reveal what the new woman in his life does for a living.moreless
Sheldon finds out that the repairs to Amy's apartment have been completed for weeks, while Leonard discovers that Penny has been removing his collectibles from the apartment.
Feeling his fetal offspring kick sends Howard on a baby-items buying binge with Raj; Sheldon and Amy host a brunch in their new digs; and Penny, by virtue of her performance in Serial Ape-ist, is invited to a sci-fi convention.moreless
While her apartment is being fixed due to a flood, Amy decides to move in with Sheldon, who sees this as a scientific experiment. Meanwhile, Howard and Bernadette find out that Raj knows what sex their baby is and they wonder whether or not they want to know.moreless
While trying to meet the Air Force deadline, Sheldon tries an energy drink for the first time and starts to believe he has become an addict. Meanwhile, Amy takes Penny to a party thrown by one of her colleagues and Bernadette thinks something is wrong with her as she's not as excited for her new baby as everyone else is.moreless
The guys heads are in a spin when an Air Force bigwig approaches them about their revolutionary gyroscope invention; and Bernadette is upset with Penny after she accidentally leaks a secret to Bernadette's coworkers about her being pregnant.moreless
As the chaotic possibility of a looming romantic relationship between Lenard's father and Sheldon's mother causes strife amongst the families, Howard's paranoia grows as he contemplates the desires of the U. S. Air Force towards him and his invention.moreless
Tensions arise when both of Leonard's parents and Sheldon's mother arrive to attend Leonard and Penny's second wedding ceremony, as they were not at the first one is Las Vegas.
Wanting to go out with the guys, Sheldon foolishly pays Stuart to spend the day with Amy. Also, Penny struggles to connect with her new mother-in-law while Amy and Bernadette have no problem hitting it off with her.moreless
The gang goes to a wine bar and runs into Penny's old boyfriend, Zack, who hits it off with Raj's girlfriend, Claire. Meanwhile, Bernadette and Sheldon spend an evening together.
While out at a cabin in the woods, Sheldon, Leonard, Penny and Amy play a game of "Never Have I Ever" which reveals some of their deep dark secrets. Meanwhile, Howard starts to believe that Raj is getting way too involved with Bernadette's pregnancy and tries to think of the nicest way to tell him to stop.moreless
When filing for a patent for their infinite persistence gyroscope, Leonard, Sheldon, and Howard learn that the university owns 75% of the patent's revenue, so they decide to write a contract between the three of them to split the remaining 25%. Also, Raj looks to the ladies for advice when both Emily and Claire contact him.moreless
Sheldon has always hated birthdays due to many bad experiences when he was younger, so the gang tries to throw him the best birthday party ever, which includes getting Adam West to appear at the party.moreless
Bernadette shares with Howard that she's pregnant, but his reaction is not what she hoped for. The guys take Howard to a karaoke bar where they are joined by the girls to celebrate the news.moreless
Sheldon and Amy host a live Valentine's Day episode of "Fun with Flags", Leonard and Penny look for a way to enjoy Valentine's Day, Howard and Bernadette prepare to try out their new hot tub and Raj struggles with his feelings about Emily.moreless
Sheldon's grandmother, aka Meemaw, visits and there's friction between her and Amy, which intensifies after the elderly woman blurts out a secret about Sheldon. Meanwhile, Raj is conflicted when an attractive writer for a children's sci-fi show asks to collaborate with him.moreless
After the entire gang was abused by a sick Sheldon, they plan a weekend getaway without him. Meanwhile Sheldon, in his own way, sets out to apologize to everyone he mistreated.