'The Big Bang Theory': Anatomy of the 100th Episode (Exclusive)

Big Bang Theory Cuoco Bed - H 2012

Big Bang Theory Cuoco Bed - H 2012

[Warning: This story contains spoilers from Thursday's "The Recombination Hypothesis" episode of The Big Bang Theory.]

The concept for Thursday's 100th episode of The Big Bang Theory -- in which Leonard (Johnny Galecki) and Penny (Kaley Cuoco) reunite -- started well before Thanksgiving with an email from Chuck Lorre to Bill Prady and Steve Molaro.

Lorre's initial intention, Prady tells The Hollywood Reporter, was to bring the show full circle back to the pilot and tell a dual what-if dream story exploring what their lives could have been like if Leonard had asked Penny out upon meeting her when she first moved in across the hall.

"Chuck had proposed a very big dream sequence episode -- possible futures -- of what would happen if they married," says Prady, who co-created the CBS comedy with Lorre. "It also had a Rashomon aspect to it because it was his dream and her dream. That was the starting place."

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The result was "The Recombination Hypothesis," a unique installment in which it's revealed late in the episode that the on-again/off-again couple's reunion took place in Leonard's mind -- until, that is, he turns it into a reality and asks Penny out on an actual date, thus reuniting the couple.

Prady and executive producer Molaro agree the concept was a risky one, and reveal that none of the exec producers wanted to cheat the audience with a disposable dream sequence episode that was "big for big's sake" and failed to advance the story.

"[It] would have not felt like an episode of our show," Molaro says.

Prady recalls that the episode evolved to its current incarnation, with Leonard starting and ending the installment at the same place in the hallway where he first spied Penny in the pilot, because the EPs wanted the half-hour to have an effect on the couple's storied relationship.

"Even with that imagining, he then moves forward and he asks her out, which is the action he takes at the beginning of the fantasy sequence," Prady says, adding that stylistically, Penny and Leonard are wearing clothing that's nearly identical to their wardrobe from the pilot.

(Another nice nod to the pilot? Leonard and Sheldon are coming up the stairs and see Penny unpacking an appliance box through her open apartment door, in what Prady calls another "mushy" moment.)

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"The thought was, if despite what had happened between you and an ex, you had gone out, it had gone badly, it went up and down, if you somehow caught her in that same moment you initially saw -- and we can all think about the moment we saw the person we're with -- and if you had that again, it would make you think," Prady says. "You get to the point where Leonard stops and thinks, 'What would happen if I ask her out again?' "

"What happens is an episode of the Big Bang Theory, and it's a legitimate, real episode in terms of structure and jokes," Prady says, adding, "and then it didn't happen, but he then goes and asks her out and begins a new story and a new chapter in dating Penny."

It's a moment that the EPs say was scripted carefully so as not to tease fans, noting the original plan was to cut to a commercial immediately after it was revealed the reunion was entirely in Leonard's imagination before coming back to see the lovable nerd really asking her out. "Our feeling was no, he's got to go immediately," Prady says. "In the same moment that the audience is going, 'Oh my God, that didn't happen," we have to say, 'Yes, but this is.' "            

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"One of the most greedy things to do is sit down and say, "Can we have our cake and eat it too? Can we do something special out of the form and at the same time can we not cheat the fans of forward progress in the story?" Prady continues. "So that's what we tried to do, and we hope it worked."

What did you think of The Big Bang Theory's 100th episode? Are you happy to see Leonard and Penny back together?

The Big Bang Theory airs Thursdays at 8 p.m. on CBS.

Email: Lesley.Goldberg@thr.com; Twitter: @Snoodit