When The Big Bang Theory’s Kaley Cuoco and Johnny Galecki Fell in Love (2024)

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 and now in paperback with dozens of new photos from the stars' personal collections and elsewhere—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.

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 sh*t, 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.

Kaley Cuoco: I knew I looked real cute in that outfit, so I was feeling really good about myself. [Laughs] And I knew he thought I looked cute because he commented on how cute I looked in that outfit earlier. But I was definitely nervous before that kiss.

Johnny Galecki: I mean, Kaley Cuoco as a kitty cat? Come on!

Kaley Cuoco: All the scenes up until we actually got together in real life, it was obvious there was always something there. There was chemistry and we were crushing on each other. That was the whole first season until we actually got together for real.

Johnny Galecki: But let’s go back to how it was kissing me for the first time. I want to hear more about that. Do I kiss differently in character?

Kaley Cuoco: I was very nervous with both [the on-screen and real-life first kisses]. I mean, I was kissing him as Penny before we ever dated, and it’s weird when you have a crush on someone and you’re kissing them as actors.

The crush continued to grow stronger for Cuoco, which made filming “The Nerdvana Annihilation” later that season somewhat of a turning point. In the episode, Leonard has a dream and saves Penny in the elevator shaft. The two are literally nose-to-nose, their bodies intertwined; it would seem like a dream scenario, but the reality of the situation was that it was getting harder and harder for Cuoco to hold back her feelings.

Kaley Cuoco: It was not an enjoyable experience for me.

Johnny Galecki: First of all, print that. [Laughs] We had to be in each other’s arms—and for quite some time, because it was a bit of a stunt that we were doing. It was a whole thing, and it was a pretape since it took a little while. Kaley didn’t look freaked out at all. In fact, she looked extremely happy in those arms. That was certainly one of the moments that I think—

Kaley Cuoco: I think we fell a little in love in that elevator shaft.

Johnny Galecki: We felt something, yeah. I think that was a massive turning point [in our relationship]. At that point, both she and I knew that something mutual was felt, and that it was going to be more of a distraction from the work to try and continue to ignore it than to actually recognize it and surrender to it.

Kaley Cuoco: I was like, Uh‑oh. I was crushing so hard on him. So much so that I was like, Get me out of here, because he had to hold me up and we had to do this really close thing. Even my cheeks were really red. I was super nervous and kept thinking, Oh my God, oh my God, oh my God. I was just a nervous wreck being that close to him in the moment.

The dream sequence where Leonard was holding Penny in the elevator shaft is captured in a photograph of the pair on Penny’s refrigerator. But as executive producer Steve Molaro points out, that picture could technically never exist.

Steve Molaro (executive producer): It makes me crazy because technically that photo was from the fantasy sequence, so it shouldn’t be a real photo on her refrigerator. Unless Leonard said, “Hey, we should go re-create this image I have from a dream of mine and get in the elevator shaft and have somebody take a picture of us,” it doesn’t belong there.

Kaley Cuoco: And Leonard doesn’t have his glasses on, either! All these things are wrong with the photo, but you couldn’t really tell where we were, so it worked.

As season one was coming to an end, Cuoco’s crush on Galecki remained just that—a crush. While the four guys often hung out outside of the show, she did not. As the youngest in the group, she was off doing her own thing— or at least the guys thought she was. It wasn’t long before that all changed during one of the guys’s getaway trips to the picturesque, ritzy seaside town of Montecito, California.

Johnny Galecki: We would finish rehearsal and Kaley would just take off. She was the youngest—and beautiful, of course—and would just get into her cool car and peel out. And we’d still be standing in the parking lot talking about rehearsal. We just thought she was too cool to hang out with us. But I guess she didn’t know we were hanging out all the time. So, obviously when the guys and I went up to Montecito, she wasn’t there because we had given up on inviting her places. But we were talking about her, so I called her and left a voicemail saying, “Hey, we’re all here playing board games, drinking wine, hanging out, and Montecito is only a two-hour drive from LA.” As soon as I left that message, she called right back. She was like, “I just broke up with my boyfriend!” And she was upset.

Cuoco wanted to know where in Montecito they were—the San Ysidro Ranch, Galecki told her—so without hesitation she told him, “I’m coming! I’ll be right there.”

Kaley Cuoco: When he called me, I was at home, and I packed a bag and hopped in my car and just drove.

Johnny Galecki: I went down to the front desk and got her a cabin, which ended up being the cabin next to mine. By the time she showed up it was pretty late, and I had gone to bed. And then I got a call. It was Kaley. She said, “There’s a bug in my room.” I was like, “Yeah, probably. You’re in a cabin.” She said, “You have to come and kill it.” I said, “I’m not doing that.” Now, still to this day, I don’t know if this story is bullsh*t or not, and if she was flirting with me because she had just broken up with her boyfriend, but I did not go over to her cabin. I knew I would be contributing to a stinkerbell actress if I did that. And the whole point of the trip was for all of us to be equals and get to know one another better. So I declined the demand to go kill a bug in her room. But apart from the bug, I smelled a rat and was thinking, Is this your way of inviting me into your hotel room basically? Which she later admitted it was. That was her way of flirting that night. And poor thing, she had just broken up with her boyfriend and we all know what that feels like. But it’s such a funny story to me now and shows how clever and adorable Kaley is. You see it in her work now as a producer; she has a way of making what she wants to happen, happen. And then at a certain point, it was also what I wanted to happen. But at that point it felt a little bit premature, especially from someone who was literally jilted from a relationship four hours earlier.

Kaley Cuoco: There was definitely a bug in my room and I was flirting with him! So both were true! I was like, Ooh, this could be a good way to get him in there! But that didn’t work. [Laughs] I couldn’t believe he turned me down. I still think he turned me down because he knew what I was doing. I used the bug as an excuse, and he still did not come over.

Johnny Galecki: Well, I’m not that easy, Kaley. I’m not just a piece of meat. There’s a heart in here. There’s real blood that pumps through my veins, believe it or not. I have feelings. At least take me to dinner and a show first! Bug in her room. Jeez.

Kaley Cuoco: But we still had a really fun weekend! I miss those days of being able to do that. We did a lot of those little weekend trips together as a cast, and it was so great.

While Cuoco and Galecki didn’t act on their feelings during that particular trip to Montecito, once the dust settled from her breakup, Galecki took it upon himself to make the first move.

Johnny Galecki: I had gone over to the Smoke House Restaurant in Burbank after rehearsal. I was there for a bit when I texted Kaley because I knew she lived in the valley. I said, “Hey, I’m just having a glass of white wine. Are you nearby?” And she texted back yes and was there in like twenty minutes or something. She later told me she was like forty-five minutes away when she got that text.

Kaley Cuoco: That’s really pathetic that I just didn’t even make him wait for like ten minutes.

Johnny Galecki: Oh yeah, she just hauled ass there. It’s not pathetic; it’s really cute. And that’s when I was like, Oh, okay, there’s some mutual sharing of feelings here. And honestly, for me, those feelings just got to a point where even though I didn’t know if it was professional, I felt like not exploring those feelings was going to be more distracting professionally than not.

Kaley Cuoco: I was so excited when he texted me. I was like, Oh my God. And I knew that was going to be trouble—getting a glass of wine with him. I knew. And we kissed at the bar! It’s so dark in there that you almost feel like you can do anything, but then it was like, Uh‑oh, I think this is really going to be bad. [Laughs] We started kissing in the bar area, and then we were kissing in the parking lot. Johnny can get really in his head and want to hide, whereas I’m the direct opposite. I would have told everybody the next day at the table read. I would have announced it and said, We’re together! But he was like, “We can’t tell anyone!” So we kept it quiet. And don’t forget, it was different then. Social media was nowhere what it is now, so it was easier to keep it hidden. You didn’t know as much about people as you do now. It’s a different world.

Johnny Galecki: After that kiss at the Smoke House, she said, “You gotta come over to my house,” so I did. And then she disappeared. She came back having showered, wearing nothing but a towel, and sat on my lap. I was like, “Okay, I guess we’re dating!”

Kaley Cuoco: [Laughs] I remember being in a robe and fully clothed underneath! We obviously remember things quite differently, but I love this story.

Johnny Galecki: I promise that my version is correct. I’m only kissing and telling because Kaley loves this story.

The two “jumped right in,” Galecki says, but agreed they wouldn’t tell anyone. And they swear they never hooked up at work in their dressing rooms.

Kaley Cuoco: It’s not like we could make the excuse we were going to one of our rooms to rehearse because everyone knew I didn’t rehearse. They wouldn’t believe that. They’d be like, “That doesn’t sound like Cuoco!”

Johnny Galecki: But there was one time Chuck busted us hiding behind a car in the parking lot. It was after a show when we went outside, and we saw Chuck walk solo out of the stage. We were by some cars, and we ducked down, like kids hiding from their parents! And he totally busted us, but he was classy about it and didn’t say anything. We just didn’t want anybody to worry.

Chuck Lorre: I can’t remember that. That might be one of those things I compartmentalized like, I can’t deal with this, I don’t have the mental, emotional bandwidth to deal with an on‑set romance.

Kaley Cuoco: [Laughs] That is such a Chuck answer! But yeah, we never even had [sex] in our dressing rooms. Absolutely f*cking not. Not a chance in hell. I wouldn’t do that. I’m not in the mile-high club. None of that… Anyway, when we were dating, Johnny was very worried about ruining the fans’ outlook on Leonard and Penny, because they weren’t even dating yet at that point in the series. He was so cerebral, and I’m like, “What?! Who f*ckin’ cares?! They’re gonna be fine!”

Johnny Galecki: Ruining is a strong word. I think complicated is a better word.

Kaley Cuoco: Yeah, maybe. I was so infatuated with Johnny at that time; definitely not anymore. [Smirks]

Johnny Galecki: Wow.

Kaley Cuoco: I was just so crazy about him, I wasn’t thinking that way. But I guess in hindsight, I kind of understood. He was very protective of what the fans would think, because we wanted them to want Leonard and Penny together so badly, that if they saw us together in real life, it could ruin the fantasy.

Johnny Galecki: And if we broke up, how would that affect their acceptance of the characters? I didn’t like the idea of people feeling like, Oh, Joanie and Chachi really do love each other! At that point in my life, that felt embarrassing. I would feel differently about it today. Love is love, and you risk anything and everything for that. But at that time, it was complicated for me, and we didn’t talk about it. And Kaley was really respectful of the parameters that I had about it.

Although Cuoco and Galecki went to great lengths to keep their newfound romance a secret, several key people started to figure out something was going on.

Bill Prady: They were talking about having gone to a theater to see a documentary about water. Johnny’s taste was very eclectic, [but] at that point I was like, There’s no way that any woman on the planet goes to see a documentary about water unless she’s passionate about water, or she’s sleeping with the guy. [Laughs]

Johnny Galecki: And it was a Russian documentary on water! Not really Kaley’s jam. There were subtitles, though. Maybe I was doing it as a character thing for Leonard, I have no idea.

Nikki Lorre (second assistant director, director): Anthony Rich [first assistant director] and all of us who were part of the weekly rehearsal team figured it out, but here’s how I knew: Johnny can sleep through anything. If I had to get him for a scene, I would knock on his dressing room door and say, “Johnny? Johnny?! JOHNNY!” He sleeps like a dead person. Well, he was late one day, and we’re calling his cell phone, calling his house phone, and he’s not picking up. We started to get worried. I think I must have still been the production assistant at the time, because they sent me to his house to make sure he was okay and wake him up. But when I got there, there was this whole gate situation, and his bedroom was in the back. I call Anthony back at the studio, who hands the phone over to Kaley, and she tells me what the code is and how to get in. I remember thinking, How do you know all this, Kaley? [Laughs] But I had to bite my tongue.

Johnny Galecki: I remember that day. I forgot to set my alarm. And Nikki is banging on the sliding glass doors of my bedroom and I was like, “Oh sh*t!” That’s hilarious.

Kaley Cuoco: Yeah, we didn’t tell anyone for a long time. I don’t even know how many months later, but we were in New York, and I said to Johnny, “I think we should tell the cast. It’s starting to feel like we’re lying to them.” Johnny said, “I’m going to call Jim right now. I want to tell him.” We call Jim on speaker, and Johnny says, “I’m in love with Kaley,” or “I really want to be with Kaley,” and Jim goes, “Ah! Does she know?!” I started laughing and yelled, “Yes, I know! I’m here!” Jim thought Johnny was telling him that he liked me and was going to tell me that. It was the cutest reaction, like, Does she know?!

Johnny Galecki: I know, I was like, “Yeah, dude, we’ve been seeing . . . never mind.”

Jim Parsons: I remember getting the call and I was somewhere in LA . . . no, I think I was in Florida. Well, it doesn’t really matter, probably, but I was outdoors when I took the phone call. The biggest thing I remember was Johnny saying it won’t get in the way of work, which was nice to say. And honestly, it really didn’t.

Simon Helberg: First off, I find it hilarious that we are talking about the location of Jim at the moment he found out. It’s like when Kennedy was assassinated—you don’t forget where you were. But no, that is amazing. Johnny came over to our house to tell me and my wife. The way I feel about it now is how I felt about it then, which was I found it somewhat hilarious, the amount of gravity that was given to it, because it was not surprising. I understand things can get complicated when business relationships get personal, but it was like, “Yeah, you guys were flirting,” and then, Wait a minute; two actors in a cast? Dating?! Like, hold the front door! I’m outta here! Get Kevin Sussman! No. [Laughs] I remember being like, “. . . And?!” And then, “Is she pregnant?” No. [Laughs] But, it was not a big surprise. I think it’s funny. And I am happy that it all worked out in the sense that it didn’t throw a huge wrench into the dynamic on set after they broke up, because things can get complicated.

Johnny Galecki: Kaley was in New York, but I went over to Simon and Jocelyn’s because I said I needed to talk to them. We went out on their back porch and sat on the steps and as I took a deep breath, Joss gasped and yelled, “No! Kaley?!” I was shocked and kinda hurt, honestly. You would have thought I’d run over Jocelyn’s dog or something. She seemed so offended and concerned. I was like, “Jesus, I’m not that much of a nightmare to be with, Joss.” [Laughs] Now, I know she presumed I was going to tell them Kaley was pregnant. Jocelyn was many, many, many steps ahead of any scenario Kaley and I would have considered. She had taken it to a whole different, soap opera level. And I, not knowing that she’d made that presumption, took it quite personally that she’d have that reaction to our simply dating. I think my ego is still a little bruised. [Laughs]

Kaley Cuoco: Johnny and I did a lot of things together with Simon and his wife, Jocelyn, and I think once they saw how much we liked each other and loved each other, everyone was into it. I’m sure they were probably more worried when we broke up, which was hard, yes, but it wasn’t some traumatic thing that we brought everyone into.

Johnny Galecki: It was hard, but Kaley’s right. We never let it affect anybody, I don’t think.

Anthony Rich: If anything, they were just adorable together and so lovely to be with, both together and separately.

But after nearly two years of dating—in which they even considered getting married at one point—Cuoco and Galecki decided they were better off as friends. While the cast and crew knew they were an item, they decided not to tell them when they broke up . . . at least not right away. All the while, the public was none the wiser that they had even been a couple.

Johnny Galecki: We’re from very different worlds, but we also seem to melt into each other’s worlds in certain ways. It was a lot of fun to teach one another different things, but then when I came to wanting different things, that made things more complicated. Obviously I was interested in Russian water documentaries and she was not. No. [Laughs] I think one of the things that created a chasm between us was my strict policies of privacy, and Kaley being very, very open about her life. I was very uncomfortable with being public about it, and I think that hurt Kaley’s feelings a little bit, and I can understand that. It certainly wasn’t because I was embarrassed of her or our relationship, but I wanted to be protective of the audience’s acceptance of Penny and Leonard, and without distraction from the tabloids. I’m private in general, but it made me especially uneasy because we were working together, and the show was kind of snowballing at the time as far as viewer- ship. And at a certain point it felt like we were living this lie because we were going to award shows and functions and pretending like we’re not a couple, when in fact we were a very loving couple.

Disagreements over how public or private to be about their relationship aside, there were other factors that contributed to their decision to break up.

Johnny Galecki: For instance, I might be a bit more scrappy than Kaley. [Laughs] She’s a very elegant and fashion-minded person, and I learn a lot from her to this day. She’ll tell me where to go for a drink in New York, and it’s this gorgeous, incredible place with these incredible mixologists and things like that, as opposed to my interests, which run along the lines of going out, intentionally getting lost and talking to a stranger at a bar and getting some dirt under my fingernails. We just had very different interests in what I think we wanted from our experience of life. It’s not to say that I don’t like very nice things, but we just had different interests. But I adore the friends that we are. I think I might value my relationship with her more than any other previous relationship or relationship afterwards. Even for her to say, “A lot of these stories for this book have to do with Johnny, so let’s get him on our Zoom” . . . I mean, that’s awesome. We just have such a bond that I appreciate so much. And I think that’s part of our great friendship.

Kaley Cuoco: Johnny and I also ran out of things to talk about, because we’d be at work all day, and then we’d go back to one of our places together, and say, “So how was your day? Simon was funny today, right?” And we’d laugh because we had no mystery. But we were together for a long time. We really adored each other, and we were lucky because as our breakup was happening, there was no foul play, there was nothing bad about our relationship . . . it just ended. Yes, there was some hurt there for a bit, but it didn’t take us that long to go back to what we were before we were dating and be friends. He was front row at both of my weddings, and we’ve been so supportive of each other ever since. We adore each other.

Johnny Galecki: We continue to love one another, just in other ways. And here’s the other thing, but when people know that you’re in a relationship, they also know when and if that relationship ends whether you’re in the public eye or not. I think this is one of the reasons people keep romantic relationships under wraps for some time. I mean, yes, it’s fun to share a dirty little secret with your new partner, but also, if the relationship ends, it can cause a lot of embarrassment and distraction during a time that’s already emotionally difficult. To be honest, maybe a love like that should be beyond the abilities to deny it. Though my intentions were always caring and protective, I certainly see in hindsight the damage that my stubborn stance might have caused. But that said, I can’t say I regret anything. I was working with the tools I had at the time.

Shortly after Cuoco and Galecki broke up in the spring of 2010, the writers were also writing toward a Penny and Leonard breakup. It was just a coincidence.

Bill Prady: I remember being worried because we were on a trajectory towards a Leonard and Penny breakup, and being concerned that I didn’t want to hurt somebody who had been through that recently. But they were amazing. I remember Kaley mentioning something we had written, and her telling us it was surprisingly accurate to something they’d gone through.

Kaley Cuoco: Too many things felt oddly similar! I used to think there were cameras in our houses since things felt eerily close to home.

For as well as Cuoco and Galecki handled their breakup, it took time. Ironically, it was a work commitment that helped speed up the healing process.

Johnny Galecki: I remember so vividly sitting in my dressing room reading a book when I was told Kaley and I would be interviewing each other for a special feature on the season three DVDs. I don’t think it had even been a week since we had broken up, and I was like, Oh f*ck, are you kidding me? Nobody knew we had broken up. So we went downstairs and cracked each other up so much to the point she nearly peed her pants, she laughed so hard. I walked out of the interview, and thought, OK, we’re going to be all right. It was a really beautiful moment, a definite turning point.

Kaley Cuoco: I do remember that. We very seamlessly made our way through that time.

But unlike their characters, at no point did they try to get back together after they broke up.

Kaley Cuoco: No.

Johnny Galecki: I changed my number immediately.

Kaley Cuoco: [Laughs] Amazing.

The cracks in their characters’ relationship are evident in that moment, but it wouldn’t be until the next episode—season three, episode twenty, “The Spaghetti Catalyst”—that it would become official.

Nikki Lorre: In one of the first episodes that Anthony Rich directed, they wrote a scene of Penny and Leonard breaking up, and the scene was in the laundry room, and it was really hard for Johnny and Kaley because they felt like they [the writers] were reading too much into their own relationship and the words weren’t crediting Leonard and Penny’s relationship as much. It went all the way up to the writers room, I believe, and the writers had to explain this wasn’t a comment on Kaley and Johnny’s relationship. They said to trust them because they were honoring Leonard and Penny. Johnny and Kaley took it very, very seriously, but even with that, they never blew up or got defensive or dramatic. They persevered in what I can only imagine was a really hard, awkward situation to work through.

Kaley Cuoco: I remember being very, very emotional during that episode, and especially during those specific scenes. I think I needed to cry.

Penny and Leonard’s relationship might have been over, but then again, it never really was. As with many modern couples, they frequently hooked up or got back together. But when they did wind up in bed again, Cuoco and Galecki were convinced it was Chuck Lorre’s doing as a way to mess with them.

Kaley Cuoco: All of a sudden, we started noticing there were extra makeout scenes for our characters, and/or sex scenes. I was like, “I think Chuck is f*cking with us!” We were convinced. Convinced! Like, Yeah, they want to date and break up on my show, well, here you go! and he was writing all the little doodads in there.

Johnny Galecki: Even though it was organic for the characters, I think he would f*ck with us. [Laughs] If it was an accident, it was a very timely accident.

Chuck Lorre: No. Not at all. Making a good show has no room for f*cking with anybody. There’s no Let’s mess with Kaley and Johnny. The goal was to make a great show and make every minute of every episode count. And that was the only goal. We don’t have that kind of freedom to risk a TV series that you put your heart and soul into to mess with somebody’s head. No. But I think that’s charming that they think we had the mental capacity to mess with them. [Laughs] Penny and Leonard having difficulty sustaining a relationship was one of the reasons to keep watching—to see if they could make it. You were rooting for them to find happiness.

Johnny Galecki: I guess that was pretty egotistical of us to think that. [Laughs] We were reading into things a little too much. I’m going to sleep a little easier tonight.

Kaley Cuoco: You are right, that’s so self-involved of us. But I am glad we know now because Johnny and I have joked about that for a long time. He’s right, though—he was too busy to f*ck with us! I’m glad we don’t have to bring that up anymore.

But around six months after Cuoco and Galecki broke up in real life, Cuoco decided to open up about their relationship for the first time in an interview with CBS’s Watch magazine in September 2010. The story went viral, with fans stunned that the two were a real-life item. Now, Cuoco looks back on how she didn’t plan on admitting something so personal, and Galecki’s reaction to the story.

Kaley Cuoco: It wasn’t like I decided, Hey, this will be the magazine that I tell! It was so not that way. I mean, why would I choose Watch magazine? I’m sorry. It was just an interview, and then the writer started asking me, and I was like, “Yeah [we were in a relationship].”

Johnny Galecki: I was outside having my coffee and my cigarette when she shoved the magazine in my face. [Laughs] And all I could say was—and I am proud of this moment—“The photos of you are beautiful.” And then I gave it back to her.

Kaley Cuoco: Johnny was like, “Why didn’t you tell me?” I said, “I didn’t even think it was a big deal.” And then when I saw the way it was written, it wasn’t what I expected. I really didn’t think of it that way, so I guess that’s why I didn’t say anything for a while.

Johnny Galecki: It truly didn’t bother me. And this is such a testament to my relationship with Kaley . . . we really handled that time very, very well.

And they did. The characters would go on to have two weddings on the show, which for any other former real-life couple could be weird, but was the complete opposite for Cuoco and Galecki.

Johnny Galecki: It wasn’t weird. A wonderful thing about walking onto the stage, much of the time, was that I got to leave all my personal drama behind. I had to. But you would think it might have been weird given there was a time Kaley and I did consider marrying, so those scenes would have been complicated at the very least. But she and I are seasoned professionals, and we’ve been doing this since we were kids, so we used it as a bit of therapy.

Kaley Cuoco: Johnny and I got so close through the show and our experiences. There was such a comfort level, and he always was so supportive of me. We had a lot of talks where I’d be like, “I don’t know about this,” and then we’d go outside and have a chat. Whatever I needed. We would almost finish each other’s sentences. We knew each other’s characters so well, but he was just constantly a steadfast person in my life, on that show, on that set. I also knew if things weren’t going well on set and if someone didn’t like something, he and I were always 99.99 percent on the same page. Except for the one fight we got into. Do you remember?

Johnny Galecki:

At this moment—perhaps as a way to take the focus off Galecki’s emotions— Cuoco throws out a memory of a ridiculous fight they got into over—of all things—tuna fish.

Kaley Cuoco: We got into a fight because he was eating tuna during the scene and I got pissed. It was a day Johnny was late, so I was already annoyed. And he decides during the scene, which did not contain food, that he was going to rehearse and eat tuna.

Johnny Galecki: I was trying to lose weight for a play I was doing at the time. Which I dedicated to Kaley, by the way. [Laughs] I even said to Jim, “Does this tuna bother you?” And he said, “No, I don’t give a sh*t.” And then Kaley walked in and said, “Oh my God! What is that f*cking smell?!” I was like, “It’s my f*cking tuna, man.”

Kaley Cuoco: [Rolls her eyes] It smelled so horrendous, and finally I was like, “I can’t do this scene with you. This is disgusting. Go eat somewhere else and then come back and do it.” So Johnny walked off and threw his tuna in the trash. He was like, “Fine!” We both stormed off. I was like, “I’m not working with tuna-head today. I just can’t.” I mean, I was livid. And Johnny was like, “Is that how you talk to me? I needed my food!” It was so dumb, but we were pissed at each other. He called it Tuna-Gate. But here’s the thing . . . after twelve years together, we were practically married. We spent so much time together. I always knew Johnny and I were good. He was always going to have my back and vice versa. No matter what. That’s what made him a good scene partner and friend. And during all the other stuff, like the [salary] negotiations, Johnny and I were very tight through that. We said, “We are all one team, and there’s nothing I don’t know that Johnny knows and vice versa.” We told them very early on to just consider us one. And that’s what we did.

Excerpted from THE BIG BANG THEORY: The Definitive, Inside Story of the Epic Hit Series. Copyright © 2022 by Jessica Radloff. Reprinted with permission of Grand Central Publishing. All rights reserved.

Jessica Radloff is Glamour's senior West Coast editor.

This story has been updated for the paperback edition of the book.

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