Leonard and Sheldon are brilliant physicists – geniuses in the laboratory but socially challenged everywhere else. Enter beautiful, street-smart neighbor Penny, who aims to teach them a thing or two about life.
When Amy's apartment floods, she proposes a cohabitation experiment with Sheldon. Also, Howard and Bernadette are upset when Koothrappali learns the gender of the baby before they do.
First Air Date: 10/10/2016