"The Big Bang Theory" star Kaley Cuoco (36) says she fell in love with her fellow actors Johnny Galecki (47) early on on the set of the series.

"I didn't even hide it. He has such amazing charisma," says the 36-year-old in a new book about the series, which was quoted by Vanity Fair magazine.

The two were in other relationships at the time, but she only had eyes for Galecki, Cuoco said: "When I found out that he also had his eye on me, I thought: oh oh, this will be trouble give."

Galecki was also quoted in Vanity Fair: "I have a healthy ego, but I need a punch in the head to know I'm being flirted with. Before Kaley and I started dating, I had no idea I had a crush was."

The internationally successful US sitcom "The Big Bang Theory" about six weird scientists (one of them played by Johnny Galecki) and a pretty waitress (Kaley Cuoco) has received multiple Emmy awards. The series started in 2007 and was shown in Germany from 2009. Cuoco and Galecki dated from 2008 to 2010, according to Vanity Fair. They were also together in the series.