Kaley Cuoco and Johnny Galecki share how they fell in love while making 'The Big Bang Theory,' from flirty texts to a sexy cat costume

According to the oral history book, "The Big Bang Theory: The Definitive, Inside Story," Cuoco was instantly drawn to Galecki.

"I had a very big crush on Johnny early on," Cuoco said in the book. "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."

"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," Galecki said. "I had zero idea of any sort of crush before Kaley and I began dating."

"I knew I looked real cute in that outfit, so I was feeling really good about myself," Cuoco recalled. "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."

About the scene, Galecki added: "I mean, Kaley Cuoco as a kitty cat? Come on!"

In the dream sequence, Leonard saves Penny in the elevator shaft and they kiss. But in reality, they were nose-to-nose for hours shooting the sequence. It was there when Galecki began to feel what Cuoco was already feeling.

"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 recalled. "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—"

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

"We felt something, yeah," Galecki continued. "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."

Cuoco had just broken up with her boyfriend when Galecki invited her to the seaside town of Montecito, California to hang out with the cast. She admits she tried to get Galecki to come to her room the first night, but he declined.

"I went down to the front desk and got her a cabin, which ended up being the cabin next to mine," Galecki said. "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 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."

"There was definitely a bug in my room and I was flirting with him!" Cuoco said. "So both were true! I was like, Ooh, this could be a good way to get him in there! But that didn't work. I couldn't believe he turned me down. I still think he turned me down because he knew what I was doing."

"I had gone over to the Smoke House Restaurant in Burbank after rehearsal," he said. "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."

"I was so excited when he texted me," Cuoco said. "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."

"We started kissing in the bar area, and then we were kissing in the parking lot," she continued. "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."

"After that kiss at the Smoke House, she said, 'You gotta come over to my house,' so I did," Galecki said. "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!"

"I remember being in a robe and fully clothed underneath!" Cuoco said. "We obviously remember things quite differently, but I love this story."

I promise that my version is correct," Galecki added. "I'm only kissing and telling because Kaley loves this story."

"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," Cuoco said. "He was so cerebral, and I'm like, 'What?! Who fuckin' cares?! They're gonna be fine!'"

"And if we broke up, how would that affect their acceptance of the characters?" Galecki said. "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."

"We're from very different worlds, but we also seem to melt into each other's worlds in certain ways," Galecki said. "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."

"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," he continued. "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."

"Johnny and I also ran out of things to talk about, because we'd be at work all day," Cuoco said. "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."

"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," Galecki said. "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."

"Johnny and I got so close through the show and our experiences," Cuoco said. "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."