Season
Episodes
Pilot
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.
The Big Bran Hypothesis
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.
The Fuzzy Boots Corollary
Leonard asks a woman out after he finds out that Penny is seeing someone.
The Luminous Fish Effect
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.
The Hamburger Postulate
Fearing he's wasting his time on Penny, Leonard ends up making a connection with Leslie.
The Middle-Earth Paradigm
Penny hosts a Halloween party, putting Leonard, Sheldon, Wolowitz, and Koothrappali through a new test of their social skills.
The Dumpling Paradox
With Wolowitz AWOL with one of her friends, Penny's recruited to fill in for him on the guys' Halo team
The Grasshopper Experiment
Raj's parents set him up on a blind date, but just when he discovers he can talk to her, she shows interest in Sheldon.
The Cooper-Hofstadter Polarization
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.
The Loobenfeld Decay
Leonard and Sheldon each lie to avoid seeing Penny's concert, but Sheldon's is a bit too complicated for his own good.
The Pancake Batter Anomaly
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.
The Jerusalem Duality
With Sheldon rattled over meeting Dennis, a 15-year-old physicist who's smarter than he, Leonard helps him look for a way to debunk Dennis's research.
The Bat Jar Conjecture
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.
The Nerdvana Annihilation
When delivery of another collectible leads to Penny's lashing out at Leonard, he decides it's time to give up his habit, much to his friends' protestation.
The Pork Chop Indeterminacy
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.
The Peanut Reaction
Penny wants to throw a surprise party for Leonard, but Sheldon's indulgence at an electronics store throws her off-track.
The Tangerine Factor
Penny's break-up spurs Leonard to summon the courage to ask her out, and each goes to Sheldon for advice on their upcoming date.
Cast
Johnny Galecki
Leonard Hofstadter
Jim Parsons
Sheldon Cooper
Kaley Cuoco
Penny
Simon Helberg
Howard Wolowitz
Kunal Nayyar
Rajesh Koothrappali
Melissa Rauch
Bernadette Rostenkowski
Mayim Bialik
Amy Farrah Fowler