Kaley Cuoco and Johnny Galecki fell in love filming this 'Big Bang Theory' scene

Kaley Cuoco and Johnny Galecki open up about their off-screen romance like they never have before in a new oral history about The Big Bang Theory. The actors, who dated from 2006 to 2008, detail how they fell in love, who made the first move and why they ultimately broke up in the forthcoming book The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series.

"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," Cuoco shares in an excerpt obtained by Vanity Fair. Galecki says he "had zero idea of any sort of crush before Kaley and I began dating."

Cuoco and Galecki's characters, Penny and Leonard, kiss for the first time in episode 6 of the show's first season. It was the first time the actors locked lips, too.

"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 recalls, admitting she was "very nervous" when they kissed for the Halloween episode.

"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," she explains. While it took months for the two to eventually kiss off camera, it soon became apparent — even to Galecki — they had a connection.

While filming "The Nerdvana Annihilation" episode later in Season 1, Cuoco and Galecki had to film a dream sequence that Leonard saves Penny in the elevator shaft.

"It was not an enjoyable experience for me," Cuoco says.

"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," Galecki recalls. "That was certainly one of the moments that I think—"

"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]. 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," Galecki confirms.

Cuoco eventually split from her boyfriend, and hours after they broke up, she joined Galecki and the rest of the cast on a trip to Montecito, Calif. They all had separate cabins, but the actress tried to get Galecki over to hers by calling and asking him to come kill a bug.

"Now, still to this day, I don’t know if this story is bullshit 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," Galecki declares.

"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," Cuoco 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."

Galecki ended up making the first move not too long after that trip when he invited Cuoco to meet for a glass of wine.

"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," Cuoco recalls. "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."

The actors told the cast and crew eventually and no one was that surprised. Galecki and Cuoco's relationship was serious — "Kaley and I did consider marrying," he says at one point — but his need for privacy ultimately contributed to the pair's break up.

"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 explains.

"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," he continues. "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."

Galecki continues, "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 viewership. 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."

While Galecki says they "had very different interests in what I think we wanted from our experience of life," that didn't stop them from becoming close friends after the split.

"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," he shares.

Cuoco didn't seem to dispute his take on the break up, but added more context.

"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," she remembers.

"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," Cuoco continues. "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."

Galecki still keeps his private life under wraps. The actor split from model Alaina Meyer in 2020. They share one son. As for Cuoco, she is dating Ozark actor Tom Pelphrey. They walked the red carpet together at the 2022 Emmy Awards, so it seems they don't disagree on being open about their relationship.