The Recombination Hypothesis
Leonard and Penny attempt to restart their relationship.
The Recombination Hypothesis is the 100th episode of *The Big Bang Theory* and the 13th of its fifth season. It aired on CBS in the United States on January 19, 2012. In the episode, Leonard spontaneously asks Penny out to dinner.
The story was conceived by series co-creator Chuck Lorre, with the teleplay written by co-creator Bill Prady and writer Steven Molaro. Mark Cendrowski directed. Critics generally responded positively, praising how Leonard and Penny tried to rework their relationship. The broadcast drew 15.71 million U.S. viewers and a 5.3 rating in the 18–49 demographic, according to Nielsen.
The plot begins with Sheldon receiving a cardboard cutout of Spock, only to be disappointed it depicts Zachary Quinto’s version rather than Leonard Nimoy’s. While he complains, Leonard sees Penny and they exchange smiles. He asks if she has dinner plans; surprised, she accepts. As Penny nervously tries on clothes with Amy and Bernadette, Bernadette reassures her that Leonard is crazy about her. Meanwhile, playing Settlers of Catan, Sheldon, Howard, and Raj question why Leonard would re-enter a relationship with Penny, given they broke up two years earlier when things got too serious for her.
At dinner, Leonard and Penny find their first date in two years awkward and decide to pretend it’s a real first date. They discuss their work, and Penny is amused when Leonard boasts about building a Bat-Signal and calling himself the “King of Nerds.” Leonard then asks if they will get back together. Shocked, Penny says she will always have feelings for him but that he overthinks everything. Offended, Leonard returns home dejected.
Later, Leonard is awakened by a text from Penny. She meets him in the hallway, kisses him, takes him into her apartment, and tells him to be quiet. Leonard wonders how a bad date ended in sex. Penny thought things were great until he asked about getting back together. Leonard suggests they try being together without telling their friends until they know it’s working, treating the relationship like a new software version: “Penny and Leonard 2.0.”
At The Cheesecake Factory, the group discusses how the date didn’t work out. Leonard sits down and starts an argument with Penny by insulting her. That night, Penny demands to know why he was a jerk, since they agreed to be friends. Leonard heads toward her apartment because their new relationship i
- episode_number
- 13th of season 5, 100th overall
- air_date
- January 19, 2012
- network
- CBS
- series
- The Big Bang Theory
- director
- Mark Cendrowski
- story_by
- Chuck Lorre
- teleplay_by
- Bill Prady and Steven Molaro
Quick Facts
- Series
- The Big Bang Theory
- Season
- 5
- Episode
- 13
- Director
- Mark Cendrowski
- Teleplay
- Bill Prady / Steven Molaro
- Story
- Chuck Lorre
- Production
- 3X6863
- Airdate
- 2012-01-19
- Length
- 22 minutes
- Guests
- Jim Turner as Reverend White
- Prev
- The Shiny Trinket Maneuver
- Next
- The Beta Test Initiation
Facts from the source article.
Lore & Background
The episode begins with Sheldon receiving a cardboard cut-out of Spock but being dismayed it is Zachary Quinto's Spock, not Leonard Nimoy's. Leonard sees Penny and asks her to dinner; she accepts. While preparing, Penny gets advice from Amy and Bernadette. Leonard's friends question why he would restart a relationship that ended two years ago. During dinner, Leonard and Penny find the date awkward and decide to pretend it is a first date. Leonard asks if they will get back together; Penny says he overthinks everything, and he leaves dejected. Later, Penny texts Leonard, kisses him in the hallway, and takes him to her apartment. They agree to keep their relationship secret until it works, calling it 'Penny and Leonard 2.0'. At The Cheesecake Factory, Leonard insults Penny, leading to a fight. Later, they reconcile with sex after fighting. Leonard then asks what they are doing, and Penny reminds him he overthinks everything. It is revealed the entire sequence was a daydream; Leonard is still with Sheldon complaining about the Spock cut-out. Despite the imagined bad outcome, Leonard decides to ask Penny out. She asks if he has thought it through; he says yes, and she agrees. In Penny's bedroom, she daydreams of being heavily pregnant at a wedding with Leonard, then decides to go to the drugstore before the date.
Reader's Guide
The Recombination Hypothesis is significant as the 100th episode of The Big Bang Theory and the first of a two-episode arc focusing on Leonard and Penny restarting their relationship, a central plot line of the series. The episode is notable for being the first in the series to use an entire dream-sequence as a storytelling device, a technique previously used on Chuck Lorre's other show Two and a Half Men. The episode received generally positive reviews, with critics praising the focus on Leonard and Penny's relationship as a fitting tribute to the series' history. It garnered 15.71 million viewers and achieved the best-ever ratings in the adults 25-54, adults 18-49, and adults 18-34 demographics. The episode required approval from Paramount, J. J. Abrams, and Zachary Quinto to mock Spock. The first scene salutes the original pilot, with Leonard and Sheldon climbing stairs in similar outfits and Penny wearing the same shirt.
Did You Know?
- The episode is the 100th overall episode of The Big Bang Theory.
- The entire episode is a dream-sequence, a first for the series.
- Approval from Paramount, J. J. Abrams, and Zachary Quinto was required to mock Spock.
- The first scene salutes the original pilot with similar outfits and Penny's shirt.
More in The Big Bang Theory episodes 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record