Physicists Leonard and Sheldon find their nerd-centric social circle with pals Howard and Raj expanding when aspiring actress Penny moves in next door.
1 The Bad Fish Paradigm 22mPenny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant.
2 The Codpiece Topology 21mA jealous Leonard reacts to Penny's new guy by rebounding with Leslie.
3 The Barbarian Sublimation 21mSheldon creates a monster when he introduces Penny to online gaming.
4 The Griffin Equivalency 21mRaj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.
5 The Euclid Alternative 20mLeonard and his friends stage an intervention to force Sheldon to face his fear of driving.
6 The Cooper-Nowitzki Theorem 21mSheldon and the gang are confused when a young grad student is attracted to him.
7 The Panty Piñata Polarization 21mWhen Sheldon bans Penny from the apartment for numerous minor infractions, she decides to retaliate.
8 The Lizard-Spock Expansion 20mLeonard inadvertently steals away the new woman Wolowitz thinks is the love of his life.
9 The White Asparagus Triangulation 21mSheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards.
10 The Vartabedian Conundrum 21mLeonard asks Penny for advice when his new relationship starts moving too fast.
11 The Bath Item Gift Hypothesis 21mPenny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette.
12 The Killer Robot Instability 21mPenny'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.
13 The Friendship Algorithm 21mSheldon creates a scientific procedure for making friends.
14 The Financial Permeability 22mSheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend.
15 The Maternal Capacitance 22mLeonard and Penny are drawn together after a disastrous visit from Leonard's mother.
16 The Cushion Saturation 21mA paintball game leads to a fight between Sheldon and Penny, and romance for Leslie and Wolowitz.
17 The Terminator Decoupling 21mLeonard, 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.
18 The Work Song Nanocluster 21mPenny's home business turns into a complete nightmare when Sheldon takes over.
19 The Dead Hooker Juxtaposition 20mPenny squares off with a new beautiful female neighbor who may become the building's "new Penny."
20 The Hofstadter Isotope 20mA fellow comic book enthusiast's hitting on Penny leads to Leonard and Howard going to a bar's Ladies' Night.
21 The Vegas Renormalization 22mLeonard and Koothrappali escort a heartbroken Wolowitz to Las Vegas, and Sheldon becomes locked out of his apartment and must stay with Penny.
22 The Classified Materials Turbulence 19mPenny'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.
23 The Monopolar Expedition 21mThe guys' plan to work over the summer at the North Pole makes Penny revaluate her feelings for Leonard.