Kaley Cuoco and Johnny Galecki Reveal the 'Big Bang Theory' Episode That Started Their Real-Life Romance

The former co-stars remained close friends after their breakup, and are now spilling details about their off-camera relationship.

Kaley Cuoco and Johnny Galecki are kissing and telling! The former Big Bang Theory co-stars are opening up like never before about their on and off-screen romance as part of a new oral history on the iconic sitcom. 

In a joint interview for the book The Big Bang Theory: The Definitive, Inside Story, excerpted by Vanity Fair, the actors detail events leading up to their real-life hookups and eventual breakup -- including the series episode where they first "fell a little in love."

"It was not an enjoyable experience for me," Cuoco says of filming the 2008 season one episode, "The Nerdvana Annihilation," in which a dream sequence sees Galecki's Leonard saving Cuoco's Penny in an elevator shaft. The two ended up face-to-face, in an embrace, for a lengthy pre-tape session. 

"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," Galecki says. 

"I think we fell a little in love in that elevator shaft," Cuoco interjects. 

"We felt something, yeah. I think that was a massive turning point [in our relationship]," Galecki adds. "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."

Cuoco continues, "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."

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The Meet Cute actress admits that she had a crush on Galecki from the start of production, though they were both in relationships with other people at the time. While the duo shared their first on-screen kiss in the Halloween episode "The Middle Earth Paradigm," it wasn't until the end of the first season that they acted on their feelings in real life. 

"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," Cuoco says.

After spending a weekend together in Montecito with their castmates -- in which the then-newly single Cuoco says she tried to make a move, but was rebuffed by Galecki -- they met up for a glass of wine at a bar near the Warner Bros. lot where Big Bang Theory filmed. 

"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 20 minutes or something. She later told me she was like 45 minutes away when she got that text," Galecki recalls. 

"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," Cuoco says with a laugh. "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."

That night, the co-stars went back to Cuoco's house and, as Galecki says, "jumped right in." 

Cuoco and Galecki managed to keep their relationship quiet on-set and in public, with Cuoco declaring: "We never even had [sex] in our dressing rooms. Absolutely f**king not. Not a chance in hell. I wouldn't do that." 

Sonja Flemming/CBS

But they were eventually noticed by Big Bang Theory showrunner, Chuck Lorre. 

"There was one time Chuck busted us hiding behind a car in the parking lot," Galecki admits. "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."

For his part, Lorre says he has no memory of that interaction -- and the couple did eventually clue in the rest of the cast and crew during the course of their two-year relationship before eventually ending their off-screen romance. 

"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," Galecki says of the breakup. "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."

Today, Cuoco and Galecki remain close friends. 

Earlier this year, Cuoco met and fell head-over-heels for actor Tom Pelphrey. In an interview with ET last month, she revealed how they got together and that it was "love at first sight." 

"We have the same manager," Cuoco said, "so we met at the Ozark premiere."

Pelphrey, who played the troubled Ben Davis in the Netflix drama, was on-hand as one of the show's stars. Cuoco happened to attend as a guest of her manager that evening. 

"I went inside, I was so excited," she recalled, "and we met there -- and it was love at first sight."

The starry-eyed actress gushed, "He's the cutest of all."

Watch below for more on her current romance.