The Big Bang Theory

Brilliant physicist roommates Leonard and Sheldon meet their new neighbour 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.

Leonard asks a work colleague out after he finds out Penny is seeing someone.

Sheldon's getting fired forces him to explore what life has to offer outside physics, leaving 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 Leslie. Meanwhile, Sheldon frets over a change to his hamburger routine.

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

When Wolowitz goes AWOL with one of her friends, Penny's recruited to fill in for him on the guys' Halo team.

Raj's parents set him up on a blind date, and when he discovers he can talk to her, 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 hearing Penny sing in a production of Rent. However, Sheldon's lie becomes a bit too complicated for its 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.

With Sheldon rattled and impossible to be around after meeting Dennis, a 15-year-old physicist who's smarter than he, the rest of the guys search for a way to eliminate the threat.

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

When Leonard and the guys buy a time-machine prop from a classic 1960 movie, its arrival creates problems for Penny, and she tells the boys that their obsession with comics and toys is "pathetic."

Leonard, Wolowitz, and Koothrappali all become smitten with Sheldon's twin sister, Missy (guest star COURTNEY HENGGELER), and Leonard devises a plan to eliminate his rivals. The plan backfires, however, when Sheldon declares he will decide whom his sister dates.

Penny wants to throw a surprise party for Leonard, but Sheldon's indulgence at an electronics store throws her off-track.

Penny's breakup spurs Leonard to summon the courage to ask her out, and they both go to Sheldon for advice on their upcoming date.