The Big Bang Theory: The Cohabitation Formulation / Season: 4 / Episode: 16 (2011)

Bernadette and Howard enjoy each other's company, but Howard's having to leave Bernadette right after sex to care for his mother leaves Bernadette disappointed. She decides to ask Howard if he wants to move in with her. After a fight with his mother about being with Bernadette, Howard goes to Leonard and Sheldon's for the night. While there, he offhandedly mentions that Raj's sister Priya is back in town and Leonard immediately rushes to Raj's house. Against Raj's wishes, Leonard and Priya decide to start a long-term relationship, while Bernadette gives Howard an ultimatum: her or his mother, and Howard takes her up on her offer to move in.