Season 3

Leonard, Penny and Sheldon are gathered watching the Grinch at, Due to the upcomming Christmas festivities, Sheldon is grumpy because he doesn't like Christmas. Penny and Leonard decorate the Christmas tree and talk to each other about how they celebrate Christmas with their families. Sheldon sits at his laptop and refuses to help, but he gives them an Isaac Newton's bust as a decoration for the tree. He gets into a discussion with Leonard because he wants Newton to hang at the top.

Leonard mentions as well that his mother is coming to visit. Penny is angry that he had not told her. Sheldon points this as Penny's fear that she might not be good enough for Leonard. Then she also realizes that Leonard had not told his mother yet that he and she are together.

Leonard and Sheldon pick up Leonard's mother from the airport. She is having a lively conversation with Sheldon, and Leonard is surprised when he learns that she and Sheldon have had contact without Leonard's knowledge. Sheldon even knows of her surgery and her engagement that she hasn't even mentioned to Leonard.

In the apartment Leonard's mother Beverly eats with the four guys. She asks about Raj's and Howard's coming out, but Howard tries to convince her that he has a girlfriend. Then Penny joins them. Beverly casually mentions that she wants to get divorced because her husband cheated on her with a waitress. A waitress, of all people. Penny tries to ignore the undertone.

Penny brings Leonard's mother to the hotel. They talk about Leonard's mom's upcoming divorce, who admits to not having had sex for a long time. Penny then invites her out for a drink.

Sheldon goes into Leonard's room. He wants to comfort him, but he turns out to be very awkward.

Penny sits with Leonard's mother in the Cheesecake-Factory and shows her how to drink. Leonard's mother likes it a lot. Penny admits to her that she is sleeping with Leonard, but this does not seem to shock Beverly. But she concludes that Leonard is either ashamed of his relationship or that his mother is not important enough to him. They want to imminently get to the bottom of this and drive back to the apartment.

There Beverly questions her son on why he hasn't said anything about his relationship. But Leonard does the same. The two hug. Beverly kisses Sheldon farewell and leaves.

The next day Penny, Sheldon and Leonard bring Beverly to the airport. Beverly Leonard makes it clear that he will take good care of Penny. Leonard now tells his mother that he has now gotten over his mother not talking enough with him.