And though they split several years ago, only now has Johnny, who plays Leonard on the hit comedy, spoken for the first time about his feelings for Kaley.
He told CBS Watch! magazine: "We're dear friends, still. Kaley's not just an ex, she's a part of my life. I just don't like to speak about it
"And not because I'm trying to be enigmatic; I just worry that it will conflict with people's acceptance of Leonard and Penny. I get the curiosity, but I don't want to distract from the story."
The pair got together after their characters developed a relationship on The Big Bang Theory, and it was only after they split when Kaley, who plays Penny, decided to come clean about their off-screen romance.
Now 27, Kaley said in 2010: "We dated for almost two years. It was such a huge part of my life and no one knew about it.
"This is the first time I've ever talked about it, ever. It was a wonderful relationship, but we never spoke a word about it and never went anywhere together."
Kaley's now engaged to tennis player Ryan Sweeting, and has been busy getting VERY excited about her big day.
Meanwhile Johnny, 38, is in a relationship with actress Kelli Garner.
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