Penny and Leonard weren't the only ones drawn to each other on the CBS sitcom The Big Bang Theory.
There was an immediate attraction between Kaley Cuoco and Johnny Galecki, who portrayed the neighbors turned love interests throughout the series' 12-season run, too. The costars dated between 2008 and 2010, during the earlier seasons of the sitcom, and according to Cuoco, she "only had eyes" for Galecki.
"I had a very big crush on Johnny early on," Cuoco says in an excerpt from The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series, published in Vanity Fair. "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."
Sonja Flemming/CBS via Getty Images Kaley Cuoco and Johnny Galecki on 'The Big Bang Theory'
Galecki, for his part, was at first oblivious. "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," he says. "I had zero idea of any sort of crush before Kaley and I began dating." Still, the onscreen chemistry that led to their offscreen romance was undeniable, Cuoco says.
"All the scenes up until we actually got together in real life, it was obvious there was always something there," she says. "There was chemistry and we were crushing on each other. That was the whole first season until we actually got together for real."
As the crush continued to simmer, filming season 1's "The Nerdvana Annihilation," wherein Leonard has a dream that he saves Penny in an elevator shaft, was a turning point. "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. "It was a whole thing, and it was a pre-tape since it took a little while."
"Kaley didn't look freaked out at all," he says. "In fact, she looked extremely happy in those arms." Cuoco adds, "I think we fell a little in love in that elevator shaft." Her costar says, "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."
Later, a kiss at the bar in Burbank's storied Smoke House Restaurant (the two now single) solidified the relationship. The two tried to keep the relationship on the down low on set, with Galecki recalling a time creator Chuck Lorre nearly "busted us hiding behind a car in the parking lot." Lorre's memory is a bit hazy: "I can't remember that," he says. "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."
Post-split, the two remain on good terms. "He was front row at both of my weddings, and we've been so supportive of each other ever since," Cuoco says, referring to her marriages to Ryan Sweeting and Karl Cook. (She and the latter divorced last year.) "We adore each other." Galecki concurs: "We continue to love one another, just in other ways."
Sign up for Entertainment Weekly's free daily newsletter to get breaking TV news, exclusive first looks, recaps, reviews, interviews with your favorite stars, and more.