Kaley Cuoco and Johnny Galecki have opened up about the real-life romantic relationship they shared while filming "The Big Bang Theory."

Cuoco and Galecki met on set while portraying Penny and Leonard on the CBS sitcom that ran from 2007 to 2019. The two had "chemistry" from the beginning, but didn't start dating until season one wrapped.

"All the scenes up until we actually got together in real life, it was obvious there was always something there," Cuoco admitted during an interview with Vanity Fair. "There was chemistry, and we were crushing on each other. That was the whole first season until we actually got together for real."

The duo went on to talk about the moment during filming "The Big Bang Theory" when they might have begun to fall "in love" in real life.

Kaley Cuoco and Johnny Galecki

"The Big Bang Theory" stars Kaley Cuoco and Johnny Galecki were actually in love in real life. (Rich Polk/Getty Images for Bethesda)

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In one episode, Leonard dreams that he saves Penny in an elevator shaft. At that point, Cuoco's feelings for Galecki were so strong she claimed that day on set was "not an enjoyable experience" for her.

"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 explained. "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 interrupted.

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

Johnny Galecki and Kaley Cuoco in "Big Bang Theory"

Galecki was worried about how his relationship with Cuoco in real life could affect the perception of Leonard and Penny's relationship on the show. (Sonja Flemming/CBS via Getty Images)

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Galecki and Cuoco kept their relationship under wraps for months after they began seeing each other. Galecki was worried about how their relationship in real life could affect the perception of Leonard and Penny's relationship in the show.

"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," Cuoco told the outlet.

"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!’" Galecki explained. "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."

The two eventually told members of the cast, but never went public with their relationship. Cuoco and Galecki even considered getting married to each other at one point during their two-year relationship.

Johnny Galecki and Kaley Cuoco smile for a photo

Galecki and Cuoco remained friends following their break-up. (Kevin Mazur/WireImage via Getty Images)

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The couple broke up in 2010, but have remained close friends and used their characters' relationship on the show as a form of "therapy."

"It wasn’t weird," Galecki said of continuing to film with Cuoco after the break-up. "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."