As their on-screen romance blossomed, Kaley Cuoco and Johnny Galecki kept their off-screen one a secret.
The Big Bang Theory costars, who dated from 2008 to 2010, revealed how they initially kept their relationship hidden from the rest of the cast in a new oral history of the series, The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series. After initially bonding at a weekend retreat in Montecito, Galecki and Cuoco decided to keep their romance under wraps during a group trip to Comic Con.
"We all had different hotel rooms at Comic-Con," Cuoco revealed, according to 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?"
Because the relationship was so new, the two hadn't told the rest of the cast they were dating yet, despite, as Galecki said, them being "our closest friends."
"So we would all be in the hotel lobby," he explained, "And Kaley and I would give each other a hug and pretend to say good night, and go our separate ways."
Eventually, series creator Chuck Lorre found out when Cuoco told him while the two were trying to make small talk.
"This is charming looking back, but I was on a shuttle bus with the cast and I was sitting next to Kaley trying to strike up a conversation," Lorre shared in the book. "The best I could come up with was, 'So ... what's going on with you? You got a fella? You seeing anybody?' Like, I'm her dad or something. And she starts giggling and says, 'Oh my God, you don't know?' And I said, 'I don't know what? What don't I know?' And she says, 'I'm seeing Johnny.'"
In the same book, Cuoco and Galecki recalled falling in love even before their characters did. After a fateful scene in an elevator shaft, the two realized there was mutual chemistry.
"At that point, both she and I knew that something mutual was felt," Galecki said, "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."
The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series is out now.