The Cohabitation Formulation (2011)

Bernadette and Howard enjoy each other's company, however Bernadette is upset because Howard always leaves her alone right after having sex so he can help his mother in the morning. Therefore, she asks Howard to move in with her, an idea that he initally turns down. After a fight with his mother about being with Bernadette , Howard decides to spend the night at Leonard's apartment. In the meantime, Howard changes his mind and decides to move in with Bernadette after she demands him to choose between her and his mother. However, after listening to Howard asking her to go shopping, do the laundry and take him to the dentist, she discovers that Howard is dependent on his mother. She informs him that she will not "be his mother", to which Howard replies with an innocent "Where did that come from?". Following that, Howard is seen returning to his mother's house, where he gets grounded for running away.

While at Leonard and Sheldon's apartment, Howard offhandedly mentions that Raj's sister Priya is back in town. When Leonard hears about this, he rushes to Raj's to talk to her. Against Raj's wishes, Leonard and Priya decide to start a long-term relationship. As the relationship progresses, Amy, having been told by Sheldon about Leonard and Priya and still being convinced of being Penny's BFF, comes to Penny's apartment to comfort her, even though Penny says she's fine. During dinner that night, Priya, after asking Penny about her acting career, recites an excerpt of Taming of the Shrew with Leonard, which weighs heavily on Penny. When Amy checks on her again afterwards, she breaks down crying, prompting Amy to comfort her before using electrodes to determine which brain regions are active during crying, as she plans to make a rhesus monkey cry by stimulating the analogous areas of its brain. The next day, with Leonard and Priya making a trip to Catalina island for the weekend, Raj at his home in strong disapproval and Howard grounded, Penny spends the evening with Sheldon and Amy .

Recurring character: Aarti Mann as Priya Koothrappali.

Title reference: Howard deciding to live with Bernadette.