The Big Bang Theory launched in 2007 as a show about four “nerds” and their hot, but ditzy female neighbor. By the time it bid goodbye a dozen years later, it had become a smart, socially relevant blockbuster and one of the greatest sitcoms of our time, tackling intimacy, consent, motherhood, marriage, and money. For the show’s oral history, timed to the 15th anniversary, I did 120 hours of new interviews with the creators, cast, producers, and more, including Kaley Cuoco and Johnny Galecki, who talk here candidly, sometimes tearfully—and in significant detail for the first time—about their love story offscreen and on.
Cuoco and Galecki’s characters, Penny and Leonard, ultimately got married, and had at least one child that we know of. The actors, of course, did not, but they did date exclusively for two years, from 2008 to 2010. In fact, much of the authenticity in their relationship onscreen was driven by the love and respect Cuoco and Galecki shared in real life. And when the offscreen relationship ended, their professional commitments and even their TV dialogue helped them heal. They developed a friendship that runs deep—and is in many ways the true love story of the show. Three plus years after Big Bang wrapped production, the duo are as tight as ever, which was made evident by the many Zooms that they did together for this book in order to pay homage to Penny and Leonard—and each other. Ahead, excerpts from a chapter in The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series.
From CBS Photo Archive/Getty Images.
Kaley Cuoco: I think a lot of what made Leonard and Penny work so well was my relationship with Johnny off camera, which turned into such sarcastic banter that bled into Penny and Leonard. Johnny and I’s relationship, in a way, was mimicking Penny and Leonard. They were always giving each other shit, and Johnny and I have a similar relationship—which you do after years of being together. We’ve always had each other’s backs, and you can’t lose that. And I do think it happened on-screen. It made our relationship funny and endearing.
Although Cuoco and Galecki were the most well-known stars thanks to 8 Simple Rules and Roseanne, respectively, when Big Bang launched, the two didn’t know each other. But when they met, there was an immediate connection—and for Cuoco, a desire for something more.
Kaley Cuoco: I had a very big crush on Johnny early on. I was so not even hiding it. He has such swagger. We were both dating people at the time, but I only had eyes for Johnny. Then, when I found out he had eyes for me too, I was like, Uh‑oh, this is going to be trouble.
Johnny Galecki: I have a healthy ego, but you really have to kind of club me over the head to let me know you’re flirting with me. I had zero idea of any sort of crush before Kaley and I began dating.
From the start, the script called for Leonard to have a crush on Penny, declaring that their babies would be “smart and beautiful.” On paper, it never should have worked—she was a gorgeous, naive, aspiring actress from Nebraska; he was a brilliant experimental physicist with no swagger, mommy issues, and a lack of confidence. But that was also the draw—two people from different worlds with an intrigue for each other (in all fairness, more so from Leonard than Penny, at least initially). It’s a classic formula that, when done right, can work so well. From Ross and Rachel to Sam and Diane to Tony and Angela, Penny and Leonard had that same potential, which became apparent in the sixth episode of the series—“The Middle Earth Paradigm”—when a drunk Penny, dressed as a sexy kitty cat, kisses Leonard at her Halloween party after her ex-boyfriend shows up. It was technically the first kiss for Cuoco and Galecki as well.