The Big Bang Theory's Leonard and Penny's romance was responsible for some of the most heartwarming moments on the show. And as is widely known, things weren't all that different behind the scenes. Johnny Galecki and Kaley Cuoco, the actors behind the iconic couple, dated for a solid two years before the show wrapped.

However, fans were left completely in the dark, only learning about the duo’s whirlwind romance nearly a year after it had ended. But, as it turns out, the two weren't exactly on the same page about why it was necessary to keep their romance hidden. So, whose idea was it to keep things under wraps?

Johnny Galecki And Kaley Cuoco Kept Their Off-Screen Romance On The Big Bang Theory A Secret

For a while, Johnny Galecki and Kaley Cuoco, two of the most widely recognized members of The Big Bang Theory's ensemble, were keeping a pretty titillating secret locked away from the world – they were an item.

“We were working together, and the show was kind of snowballing at the time as far as viewership,” Johnny Galecki shared of the romance in The Big Bang Theory: A Definitive, Inside Story, Per Us Weekly. “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.”

via CBS

Intent on keeping the 2-year romance under wraps, Galecki and Cuoco went to great lengths to avoid rousing suspicion. The two even went as far as booking separate rooms and sneaking around whenever they had to attend events for the show.

"We all had different hotel rooms at Comic-Con," Cuoco admitted, per Us Weekly. "There were two giant buildings for this one hotel and Johnny and I weren't even in the same building. So, we were like little mice in the night, running back and forth to each other's rooms, trying not to be noticed. I mean, who did we think we were?"

Given The Big Bang Theory’s immense popularity, it’s truly a marvel that the two were able to keep their romance under wraps for so long. But, as it turns out, there was one missing variable that made concealing the relationship a lot easier.

“It was different then,” Cuoco shared. “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.”

Kaley Cuoco Wasn’t Thrilled About Keeping Her Relationship With Johnny Galecki A Secret

Fans remained in the dark about Cuoco and Galecki's fling long after they’d called it quits. In fact, nobody suspected a thing before Cuoco finally spilled the juicy details in a 2010 interview with CBS Watch! Magazine.

"It was such a huge part of my life and no one knew about it. It was a wonderful relationship, but we never spoke a word about it and never went anywhere together."

Elsewhere in the interview, Cuoco admitted that she wasn't completely on board with keeping the romance a secret. “Everyone was always asking, and we deny-deny-denied.

Via: TheThings

And I'm like, 'Why am I denying this person that I love?'" she said. “That's not the kind of relationship I want — I don't want to be hiding. We couldn't do anything. It wasn't as fun as we wanted it to be."

However, according to The Flight Attendant star, Galecki was dead-set on keeping things under wraps. “Johnny can get really in his head and want to hide, whereas I’m the direct opposite,” she shared in The Big Bang Theory: A Definitive, Inside Story per Vanity Fair.

“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.”

Why Johnny Galecki Preferred To Keep His Romance With Kaley Cuoco A Secret

Johnny Galecki has never shied away from admitting just how much he adored Kaley Cuoco during their two-year relationship. The two even ended up becoming close friends after their romance ended. So, why did the Vanilla Sky actor prefer to keep the romance under wraps?

"It certainly wasn't because I was embarrassed of her or our relationship,” he admitted in The Big Bang Theory: The Definitive, Inside Story, per Vanity Fair, “but I wanted to be protective of the audience's acceptance of Penny and Leonard, and without distraction from the tabloids."

via CBS

According to Cuoco, Galecki believed that rumors of an off-screen romance with Cuoco would disrupt Penny and Leonard’s romantic storyline, which was still in its nascent stages at the time.

“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."

“He was so cerebral, and I’m like, “What?! Who f***in’ cares?! They’re gonna be fine!," Couco said.

Despite her reservations, Cuoco ultimately came to see things from Galecki’s perspective. “I was just so crazy about him, I wasn’t thinking that way. But I guess in hindsight, I kind of understood,” she explained.

“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.”

Sadly, the Roseanne star’s desire to keep things under wraps ultimately took a toll on the relationship. “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 admitted per Vanity Fair. “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.”