
Mensa-fied best friends and roommates Leonard and Sheldon, physicists who work at the California Institute of Technology, may be able to tell everybody more than they want to know about quantum physics, but getting through most basic social situations, especially ones involving women, totally baffles them. How lucky, then, that babe-alicious waitress/aspiring actress Penny moves in next door. Frequently seen hanging out with Leonard and Sheldon are friends and fellow Caltech scientists Wolowitz and Koothrappali. Will worlds collide? Does Einstein theorize in the woods?

Life gets complicated when Stuart starts bringing his new girlfriend home; Penny and Leonard talk about starting a family; Koothrappali explores an arranged marriage.

When Penny's comment about Wolowitz's love life sends him into a depressed stupor, his friends lose their most important teammate in an upcoming fighting-robot competition.

Penny tries to mediate when Sheldon and Leonard disagree on whether to present their joint findings at a physics conference.

Leonard and Sheldon try to avoid seeing Penny perform after hearing her sing, but the elaborate lie Sheldon tells leads to an unexpected result.