Pam and Jim make an embarrassing blunder after the birth of their baby. Elsewhere, Michael makes Andy jealous by setting Erin and Kevin up for a breakroom lunch date.
Sheldon enters a competition but is annoyed when he finds out that Star Trek actor Wil Wheaton is participating, because Wil cancelled his appearance at a sci-fi convention that Sheldon had attended as a child.
Wolowitz is scared about committing to Bernadette and so avoids her. He soon realises he's made a mistake and to compensate, proposes to her.
Penny feels left out when Bernadette shows an interest in science and so asks Sheldon to teach her about it. Eventually, she surprises everyone with what she's learned.
Leonard realises that he's the only one of the gang without a girlfriend, while Sheldon wants to get rid of his when she hatches a plan for him to meet her mother.