"He had regular or recurring roles on a lot of television programs. And he was being well paid and ... he said, 'Pop, I've got the best of all worlds. ..I am the best known unknown actor out here. I don't have to put up with the nonsense. I don't have to be worried about the paparazzi or any of that kind of problem. All I have to worry about is being a working actor, doing my work,'" Nick Clooney said.
Just as he got comfortable being a relative-unknown in a town of big-wigs, Clooney was tapped to play Dr. Doug Ross on a new NBC medical drama "ER." The primetime hospital serial became a smash-hit and made Clooney into a genuine A-list sex symbol.
"He was then on the cover of Newsweek magazine and the world turned upside down," his dad recalled.
"George Clooney has proven that he's more than just a matinee star on screen," said O'Neill. "He's worked behind the screen as a writer, as a director, and now he's giving these kind of full bodied emotional performances that show us he's the real deal."
Looking back on his son's early years, Nick Clooney sensed that his son's perseverance would make him a star.
"Most of us, whatever we're doing, we find a plateau. It is comfortable. We sort of stay there, kind of hone it, which George didn't do," he said. "He didn't like to be comfortable. He liked to challenge himself. He wanted to get to the next step. So being funny is good. But being good is even better, and he got better and better at everything and he continues to do that now."
Watch "Before They Were Famous," on a special edition of "20/20" tonight at 10 p.m. ET