Penny admits she fears Leonard will leave her for someone smarter. They eventually agree to stop worrying and focus on their new marriage. Sheldon’s Retaliation
The episode begins with Leonard having a nightmare where he kisses Sheldon to "restore balance" to his marriage after admitting he kissed another woman, Mandy Chow. [S9E2] The Separation Oscillation
Mandy dismisses his concerns, leading Leonard to realize he subconsciously tried to sabotage his marriage because he feels he doesn't deserve Penny. Penny admits she fears Leonard will leave her
To put Penny's mind at ease, Leonard visits Mandy (played by Melissa Tang ) at Caltech. Mandy Chow. Mandy dismisses his concerns