Brilliant physicist roommates Leonard and Sheldon meet their new neighbor Penny, who begins showing them that as much as they know about science, they know little about actual living.

Leonard volunteers to sign for a package in an attempt to make a good impression on Penny, but when he enlists Sheldon for help, his attempt at chivalry goes terribly awry.

When Leonard learns Penny is seeing someone, he decided to asks a nerdy female co-worker out on a date.

When Sheldon gets fired and decides to explore life beyond physics, it's up to Leonard to take drastic action to snap his friend out of his funk.

Fearing he's wasting his time on Penny, Leonard ends up making a connection with colleague Leslie Winkle.

Penny hosts a Halloween party, that ends up putting Leonard, Sheldon, Wolowitz, and Koothrappali through a new test of their social skills.

When Wolowitz seduces one of Penny's friend who then takes over her apartment, Penny sleeps on Leonard and Sheldon's couch. Meanwhile, Penny is recruited to fill in for Howard on the guys' Halo team.

Raj's parents set him up on a blind date, but just when he discovers he can talk to his date, she shows interest in Sheldon.

When they're invited to present at a physics conference, Sheldon's reluctance to share the credit leads to a tiff between him and Leonard, and Penny's intervention only exacerbates the situation.

Leonard and Sheldon each lie to avoid seeing Penny's concert, but Sheldon's lie is a bit too complicated for his own good.

With his friends knowing how sour he acts when sick—and avoiding him as a result—Sheldon is nursed by Penny, who hasn't a clue what she's in for.

When Sheldon meets a 15-year-old physicist prodigy, he's rattled and threatened and Leonard tries to help him look for ways to debunk his research.

Sheldon finds himself booted from the gang's Physics Bowl team and replaced by Leslie Winkle, so he forms his own team, hoping to prove he's superior.

When the guys buy a time machine prop from a classic 1960 movie, Penny lashes out at Leonard and he decides it's time to give up his habit, much to his friends' protestation.

The rest of the gang fall for Sheldon's twin sister, and Leonard's plan to win her heart is derailed when Sheldon declares he'll be the one to decide who can date her.

Penny wants to throw a surprise party for Leonard, but Sheldon's indulgence at an electronics store throws her off-track. Meanwhile, Howard makes a terrible sacrifice for the sake of the surprise.

Penny's break-up spurs Leonard to summon up the courage to ask her out, and each head to Sheldon for advice on their upcoming date.