Series 1, Episode 1

The Pilot

When Leonard and Sheldon meet Penny, Leonard is immediately interested in her.

Series 1, Episode 2

The Big Bran Hypothesis

After Leonard tries to do a favor for Penny, Sheldon ruins the plan.

Series 1, Episode 3

The Fuzzy Boots Corollary

Leonard learns Penny is dating someone and asks a woman on a date.

Series 1, Episode 4

The Luminous Fish Effect

After being fired, Sheldon attempts to explore the dreadful life beyond physics.

Series 1, Episode 5

The Hamburger Postulate

Leonard agrees to an unexpected sexual encounter.

Series 1, Episode 6

The Middle Earth Paradigm

The socially stunted guys are nervous when Penny invites them to a party.

Series 1, Episode 7

The Dumpling Paradox

When Wolowitz seduces Penny's friend, Penny sleeps on Leonard's couch.

Series 1, Episode 8

The Grasshopper Experiment

Koothrappali becomes overwhelmed when his parents arrange a blind date for him.

Series 1, Episode 9

The Cooper-Hofstadter Polarization

Sheldon and Leonard are invited to present their joint findings at a conference.

Series 1, Episode 10

The Loobenfeld Decay

After hearing Penny sing, Leonard lies to avoid seeing her perform.

Series 1, Episode 11

The Pancake Batter Anomaly

When Sheldon gets sick, Leonard and the boys avoid him like the plague.

Series 1, Episode 12

The Jerusalem Duality

Leonard and Sheldon are distraught after meeting a 15-year-old physics prodigy.

Series 1, Episode 13

The Bat Jar Conjecture

The guys decide to compete in the university's Physics Bowl.

Series 1, Episode 14

The Nerdvana Annihilation

A time-machine prop from a classic 1960 movie creates problems for Penny.

Series 1, Episode 15

The Pork Chop Indeterminacy

Leonard, Wolowitz, and Koothrappali become smitten with Sheldon's twin sister.

Series 1, Episode 16

The Peanut Reaction

Penny attempts to throw Leonard a surprise birthday party.

Series 1, Episode 17

The Tangerine Factor

When Penny breaks up with her boyfriend, Leonard asks her out on a date.