Sara Gilbert as Leslie Winkle
Episodes 9
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.
Read MoreThe Fuzzy Boots Corollary
Leonard asks a woman out after he finds out that Penny is seeing someone.
Read MoreThe 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.
Read MoreThe Hamburger Postulate
Fearing he's wasting his time on Penny, Leonard ends up making a connection with Leslie.
Read MoreThe Middle-Earth Paradigm
Penny hosts a Halloween party, putting Leonard, Sheldon, Wolowitz, and Koothrappali through a new test of their social skills.
Read MoreThe Dumpling Paradox
With Wolowitz AWOL with one of her friends, Penny's recruited to fill in for him on the guys' Halo team
Read MoreThe 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.
Read MoreThe 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.
Read MoreThe 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.
Read MoreThe 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.
Read MoreThe 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.
Read MoreThe 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.
Read MoreThe 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.
Read MoreThe 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.
Read MoreThe Peanut Reaction
Penny wants to throw a surprise party for Leonard, but Sheldon's indulgence at an electronics store throws her off-track.
Read MoreThe 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.
Read MoreThe Bad Fish Paradigm
Penny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant.
Read MoreThe Codpiece Topology
A jealous Leonard reacts to Penny's new guy by rebounding with Leslie.
Read MoreThe Barbarian Sublimation
Sheldon creates a monster when he introduces Penny to online gaming.
Read MoreThe Griffin Equivalency
Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.
Read MoreThe Euclid Alternative
Leonard and his friends stage an intervention to force Sheldon to face his fear of driving.
Read MoreThe Cooper-Nowitzki Theorem
Sheldon and the gang are confused when a young grad student is attracted to him.
Read MoreThe Panty Piñata Polarization
When Sheldon bans Penny from the apartment for numerous minor infractions, she decides to retaliate.
Read MoreThe Lizard-Spock Expansion
Leonard inadvertently steals away the new woman Wolowitz thinks is the love of his life.
Read MoreThe White Asparagus Triangulation
Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards.
Read MoreThe Vartabedian Conundrum
Leonard asks Penny for advice when his new relationship starts moving too fast.
Read MoreThe Bath Item Gift Hypothesis
Penny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette.
Read MoreThe Killer Robot Instability
Penny's criticism of Wolowitz's romantic life pushes him into depression and AWOL for a fighting robot battle the rest of guys are depending on him for.
Read MoreThe Friendship Algorithm
Sheldon creates a scientific procedure for making friends.
Read MoreThe Financial Permeability
Sheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend.
Read MoreThe Maternal Capacitance
Leonard and Penny are drawn together after a disastrous visit from Leonard's mother.
Read MoreThe Cushion Saturation
A paintball game leads to a fight between Sheldon and Penny, and romance for Leslie and Wolowitz.
Read MoreThe Terminator Decoupling
Leonard, Sheldon and Wolowitz are ecstatic to learn that a famous science-fiction actress (Summer Glau) is on board the train they are taking to San Francisco.
Read MoreThe Work Song Nanocluster
Penny's home business turns into a complete nightmare when Sheldon takes over.
Read MoreThe Dead Hooker Juxtaposition
Penny squares off with a new beautiful female neighbor who may become the building's "new Penny."
Read MoreThe Hofstadter Isotope
A fellow comic book enthusiast's hitting on Penny leads to Leonard and Howard going to a bar's Ladies' Night.
Read MoreThe Vegas Renormalization
Leonard and Koothrappali escort a heartbroken Wolowitz to Las Vegas, and Sheldon becomes locked out of his apartment and must stay with Penny.
Read MoreThe Classified Materials Turbulence
Penny's second date with Stuart sees her making a comment that gives Leonard new hope for a relationship with her. Wolowitz realizes there's a crucial error in a NASA project he's working on.
Read MoreThe Monopolar Expedition
The guys' plan to work over the summer at the North Pole makes Penny revaluate her feelings for Leonard.
Read MoreThe Electric Can Opener Fluctuation
When Sheldon learns the guys tampered with his expedition data he got from the arctic, he leaves to Texas in disgrace. This results in the guys following him, which threatens Leonard's hope for some romantic time with Penny and the guys' friendship with Sheldon.
Read MoreThe Jiminy Conjecture
Leonard and Penny struggle to recover from an awkward first hookup while Sheldon and Howard stake their best comic books on a bet to determine the species of a cricket.
Read MoreThe Gothowitz Deviation
Howard and Raj visit a Goth nightclub to pick up women while Sheldon attempts to build a better Penny using chocolate-based behavior modification.
Read MoreThe Pirate Solution
Raj must find a new job or be sent back to India, but Sheldon has a solution, which leaves Leonard and Penny dealing with Howard as a third wheel.
Read MoreThe Creepy Candy Coating Corollary
After overhearing that Wil Wheaton is entering a trading-card competition, Sheldon decides to enter it himself. Meanwhile, Penny sets up one of her friends on a date with Wolowitz.
Read MoreThe Cornhusker Vortex
Sheldon becomes Leonard's teacher in order to understand football, while an incident with flying a kite threatens Howard and Raj's friendship.
Read MoreThe Guitarist Amplification
A squabble between Leonard and Penny sees Sheldon playing mediator, though out of his own incovenience from the sitiation rather than altruism.
Read MoreThe Adhesive Duck Deficiency
With Leonard, Howard and Raj away camping in the desert, an injured Penny has only Sheldon to rely on.
Read MoreThe Vengeance Formulation
After he's humiliated on National Public Radio, Sheldon vows to destroy Kripke, while Wolowitz tries not to destroy his new relationship with Bernadette.
Read MoreThe Gorilla Experiment
Penny gets help from Sheldon in order to understand what Leonard's work is, while Wolowitz develops a jealousy when Leonard starts hanging out with his new girlfriend.
Read MoreThe Maternal Congruence
A Christmas visit from his mother has Leonard discovering she's kept a lot of news from him that she shares with Sheldon and worrying if she'll approve of his romance with Penny.
Read MoreThe Psychic Vortex
Leonard is aghast to find out a secret of Penny's: she believes in psychics. Meanwhile, Sheldon tries to assist Koothrappali in picking up a girl at a university mixer.
Read MoreThe Bozeman Reaction
When their apartment is robbed, Leonard and Sheldon turn to their friends to create a state-of-the-art security system.
Read MoreThe Einstein Approximation
Sheldon's search for the answer to a physics problem leads him to work at the Cheesecake Factory with Penny.
Read MoreThe Large Hadron Collision
Leonard can only bring one guest on a trip to see CERN's Large Hadron Collider (the world's largest and highest energy particle accelerator) in Switzerland on Valentine's Day.
Read MoreThe Excelsior Acquisition
Sheldon winds up in traffic court when he gets a ticket because of Penny.
Read MoreThe Precious Fragmentation
When the guys find a ring from "The Lord of the Rings" at a garage sale, it threatens to tear them apart.
Read MoreThe Pants Alternative
Sheldon's friends come to his aid when his fear of public speaking stands between him and a coveted award.
Read MoreThe Wheaton Recurrence
A fight between Leonard and Penny threatens their relationship, while Sheldon battles Wil Wheaton in bowling.
Read MoreThe Spaghetti Catalyst
When Leonard and Penny aren't speaking, Sheldon goes to extremes to keep them both happy.
Read MoreThe Plimpton Stimulation
Leonard and Sheldon compete for the attention of a famous female physicist.
Read MoreThe Staircase Implementation
Leonard tells Penny about how he met Sheldon for the first time...and what happened to the elevator.
Read MoreThe Lunar Excitation
While Penny worries that dating Leonard has ruined her for normal guys, Wolowitz and Koothrappali search for Sheldon's perfect match online.
Read MoreThe Matrimonial Momentum
After driving to Vegas to get married, Penny struggles with Leonard’s confession that he kissed another girl. Also, Sheldon doesn't know how to act after Amy pushes pause on their relationship.
Read MoreThe Separation Oscillation
Leonard confronts the woman he kissed on the North Sea in an attempt to set Penny's mind at ease. Also, Sheldon films a special episode of "Fun with Flags" after his breakup with Amy, and Bernadette feels guilty about withholding a secret from Penny.
Read MoreThe Bachelor Party Corrosion
The guys' science skills are put to the test when they get a flat tire during Leonard's bachelor party weekend in Mexico. Also, the girls force Penny to finally tell her family that she eloped with Leonard.
Read MoreThe 2003 Approximation
Sheldon learns of an impending change in his living arrangements and decides to revert back to 2003, a simpler time before he met Leonard and Penny. Also, Howard and Raj form a band to play at the Comic Book Store.
Read MoreThe Perspiration Implementation
The guys take a fencing lesson from Barry Kripke and Sheldon finds himself in an awkward position when Kripke expresses interest in Amy. Also, when Stuart struggles to get female customers at the Comic Book Store, Penny, Amy and Bernadette come by to help him out.
Read MoreThe Helium Insufficiency
In the midst of a nation-wide helium shortage, Sheldon and Leonard take desperate measures to get the supplies they need. Also, Penny and Bernadette download a dating app on Amy's phone to try and find her a new man.
Read MoreThe Spock Resonance
Wil Wheaton interviews Sheldon for a Star Trek documentary where he reveals the ring and his plan to propose to Amy. Bernadette wants to start renovating the house and the topic of starting a family together with Howard is brought up.
Read MoreThe Mystery Date Observation
Sheldon, Wolowitz and Koothrappali post an online advertisement to find Sheldon a new girlfriend. Also, when Amy is coy with details about a guy she is dating, Penny and Bernadette decide to spy on her.
Read MoreThe Platonic Permutation
Sheldon and Amy try hanging out as friends when they spend Thanksgiving together at the aquarium. Also, Wolowitz reluctantly agrees to volunteer at the soup kitchen with Bernadette, Raj and Emily, and Penny discovers that Leonard knows more about her than she thought.
Read MoreThe Earworm Reverberation
Sheldon has a revelation when he realizes why a song was stuck in his head. Also, Amy invites Dave over for dinner despite their previously awkward date, and Wolowitz and Koothrappali become obsessed with a fan of their band, "Footprints on the Moon".
Read MoreThe Opening Night Excitation
After more than five years of dating, Sheldon and Amy spend their first night together. Also, Leonard, Wolowitz, and Koothrappali must decide who will take their extra Star Wars movie ticket.
Read MoreThe Sales Call Sublimation
Penny gets more than she bargained for when Leonard agrees to meet with a psychiatrist on her behalf. Also, Sheldon and Koothrappali collaborate on an astronomical discovery, and Wolowitz and Bernadette can't believe what they are feeling after Stuart moves out.
Read MoreThe Empathy Optimization
After having to deal with a sick Sheldon, Leonard, Penny and the gang try to treat themselves to a Sheldon-free weekend.
Read MoreThe Meemaw Materialization
Meemaw meets Amy, but it isn't all roses. Meemaw seems to have an axe to grind with her. Sheldon comes to Amy's defense, but not before Meemaw lets a little secret of his slip.
Read MoreThe Valentino Submergence
Sheldon and Amy host a live Valentine's Day episode of Fun with Flags, Leonard and Penny grapple with getting older, Howard and Bernadette find a surprise in their hot tub and Raj is torn between Emily and the cute girl he met at the Comic Bookstore.
Read MoreThe Positive Negative Reaction
When the gang finds out about Bernadette’s pregnancy, they celebrate by singing karaoke. Also, Bernadette is concerned when Wolowitz freaks out over her pregnancy announcement, and Wolowitz is convinced he must make more money to provide for the baby.
Read MoreThe Celebration Experimentation
After more than nine years together, the gang finally celebrates Sheldon’s birthday, surprising him with a special guest.
Read MoreThe Application Deterioration
Leonard, Sheldon, and Wolowitz run into problems when they file for a patent for their infinite persistence gyroscope. Also, Penny, Amy and Bernadette give Koothrappali dating advice when Emily reaches out to him after their breakup.
Read MoreThe Solder Excursion Diversion
Amy is shocked at a revelation from Sheldon after she buys him a new laptop. Also, Koothrappali sells out Leonard and Wolowitz after they lie to their wives in order to attend an early screening of a movie.
Read MoreThe Big Bear Precipitation
Sheldon spills a secret of Leonard’s when the two take a weekend cabin trip with Penny and Amy. Also, when Koothrappali goes overboard with pregnancy gifts, Wolowitz and Bernadette must draw the line.
Read MoreThe Viewing Party Combustion
Everyone must choose sides when a small argument between Leonard and Sheldon erupts into a heated fight during a group get-together.
Read MoreThe Fermentation Bifurcation
The gang goes to a wine bar and runs into Penny’s old boyfriend, Zack. Also, Bernadette gets stuck spending the evening with Sheldon when she can’t go wine tasting with the group, and things don’t go as planned when Koothrappali introduces his new girlfriend, Claire.
Read MoreThe Line Substitution Solution
Sheldon hires Stuart to spend the day with Amy when he’d rather go to a movie screening. Also, Leonard’s mother, Beverly, comes to town and Penny struggles to make a connection with her.
Read MoreThe Convergence Convergence
Chaos ensues when Leonard’s recently divorced parents, Alfred and Beverly, and Sheldon’s devoutly religious mother, Mary, come to town. Also, Wolowitz and Koothrappali think the government is out to get them when they are contacted about their guidance system.
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