Episode 23 - The Lunar Excitation (323) While Penny worries that dating Leonard has ruined her for normal guys, Wolowitz and Koothrappali search for Sheldon's perfect match online.
Directed by Peter Chakos.
Written...
Episode 22 - The Staircase Implementation (322) Leonard tells Penny the story of how he first met Sheldon. This episode is told mostly in flashback. Leonard starts out by explaining how Sheldon's previous roommate ran out...
Episode 21 - The Plimpton Stimulation (321) Dr. Elizabeth Plimpton (Judy Greer), a cosmological physicist from Princeton University, comes to Cal Tech for a job interview. Sheldon arranges her trip, and offers her to...
Episode 20 - The Spaghetti Catalyst (320) Leonard and Penny have broken up. Sheldon meets Penny in the hall and invites himself to visit her in an hour for spaghetti with hot dogs. Faced with Howard's explanation...
Episode 19 - The Wheaton Recurrence (319) One night after having sex, Leonard surprises Penny by saying "I love you" but she can only say "thank-you" and they both start to think about where their relationship is...