Although they kept their off-screen relationship a secret at the time, Kaley Cuoco and Johnny Galecki's relationship did get off to a great start. The romance between Penny, the attractive girl, and Leonard, the geek down the hall, was one of the main stories of The Big Bang Theory. According to Entertainment Weekly, it turns out that Kaley Cuoco and Johnny Galecki, the actors who played the roles, also had a romantic attraction.

The Big Bang Theory actors, Kaley and John, recalled that their real-life romance was practically preordained. (They began secretly dating from 2008 to 2010).

Keep reading to find out more.

The two discussed their on-set romance and how it paved the way for a friendship that went beyond the hit show in an oral history of the show for Vanity Fair titled The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series.

When they started working together on the show in 2007, Kaley Cuoco acknowledged having "a very big crush on Johnny early on." The actress admitted, "I was so not even  hide it." He has such a swagger. We were dating people then, 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."

On the other hand, Galecki also felt a romantic attraction but was unaware that the flirting was genuine. It was simple to confuse life with art when the two of them were portraying characters in love, especially since Galecki freely admits that she isn't good at picking up on these cues. "I have a healthy ego, but you have to kind of club me over the head to let me know you're flirting with me," he said.

That quality unites Johnny Galecki and his on-screen persona Leonard, who shares a Pasadena apartment with his roommate Sheldon. Both are socially awkward geniuses in high-science fields. Penny, a waitress and aspiring actress played by Kaley Cuoco, moves into the apartment down the hall and builds friendships with her neighbors and friends, assimilating herself into their community.

Eventually, Leonard and Penny fall in love and start dating, and the two actors experience chemistry as their on-screen characters' love story progresses. In one episode, Leonard dreams of saving Penny from an elevator shaft, and the scene is filmed with the two close for a while.

Kaley Cuoco and Johnny Galecki dated for a while but eventually parted ways. Despite this, the two have remained close, their romantic love developing into a different kind of love. The chemistry between Penny and Leonard persisted throughout the 12-year run of the show. Galecki attended both of Kaley Cuoco's weddings, first to Ryan Sweeting and then to Karl Cook. Both of them and The Big Bang Theory continue to be the favorites of the two.