Series 1 Episode 5
Leonard worries that he's wasting his time on Penny, so he gets closer to Leslie. Meanwhile, Sheldon frets over a change to his hamburger routine.
Series 1 Episode 1
Pilot: Leonard and Sheldon's geeky world is shaken up by the arrival of a new neighbour
Series 1 Episode 1
Series 1 Episode 2
The Big Bran Hypothesis: Sheldon sneaks into Penny's apartment to tidy it, but she's not pleased
Series 1 Episode 2
Series 1 Episode 3
The Fuzzyboots Corollary: Leonard summons up the courage to ask a woman out on a date
Series 1 Episode 3
Series 1 Episode 4
The Luminous Fish Effect: Getting fired leaves Sheldon pondering life beyond physics
Series 1 Episode 4
Series 1 Episode 5
The Hamburger Postulate: Sheldon is uncomfortable with a change to his hamburger routine
Series 1 Episode 5
Series 1 Episode 6
The Middle Earth Paradigm: Penny's Halloween party puts the gang's social skills to the test
Series 1 Episode 6
Series 1 Episode 7
The Dumpling Paradox: Penny needs somewhere to sleep when Howard spends the night in her flat with her friend
Series 1 Episode 7
Series 1 Episode 8
The Grasshopper Experiment: Raj discovers that he can talk to women when he's had a few drinks
Series 1 Episode 8
Series 1 Episode 9
The Cooper-Hofstadter Polarization: Sheldon's reluctance to share credit on joint work causes a rift between him and Leonard
Series 1 Episode 9
Series 1 Episode 10
The Loobenfeld Decay: Sheldon lies to get out of seeing Penny perform on stage. But one lie leads to another...
Series 1 Episode 10
Series 1 Episode 11
The Pancake Batter Anomaly: Penny makes the mistake of volunteering to look after Sheldon when he's sick
Series 1 Episode 11
Series 1 Episode 12
The Jerusalem Duality: Sheldon's shaken when he meets a teenage physicist who is clearly much brighter than he is
Series 1 Episode 12
Series 1 Episode 13
The Bat Jar Conjecture: Sheldon is ousted from the gang's Physics Bowl quiz team, so he forms a rival team
Series 1 Episode 13
Series 1 Episode 14
The Nerdvana Annihilation: Leonard considers giving up his habit of collecting memorabilia when Penny makes fun of it
Series 1 Episode 14
Series 1 Episode 15
The Shiksa Indeterminacy: Leonard, Howard and Raj compete for the attention of Sheldon's stunning twin sister
Series 1 Episode 15
Series 1 Episode 16
The Peanut Reaction: Penny plans a surprise party for Leonard, but things don't exactly go to plan
Series 1 Episode 16
Series 1 Episode 17
The Tangerine Factor: Penny's break-up spurs Leonard to summon the courage to ask her out
Series 1 Episode 17