"That's what I knew how to do," he explained. "That guy's a little daft, lazy, getting by on his looks and not a whole lot else, and sweet, and likeable, blue-collar, that guy... funny sometimes. That's what I knew how to play."
Is that who he was?
"No, that's who I got really good at playing."
McFadden noted a misperception among some people that the man was not so different from the characters he has played.
"Good," said Kutcher. "If people can peg you and know exactly what you are, and what you are gonna bring to the table... then your opportunity becomes to disappoint them. Sometimes you can exceed an expectation, but it's a lot more work to do that."
Kutcher has put in the work. Not satisfied with just being an actor, he became a producer and co-creator of the MTV hit show "Punk'd." For it, he played brutal practical jokes on unsuspecting celebrities.
He has gone on to produce 12 TV shows in the past five years. When does he sleep? "On weekends," he said.
And of course, we all know who he goes home to. His relationship with Demi Moore, who is 47 -- 15 years his senior -- is now old news.
McFadden asked him what his biggest extravagance was.
"Neither Demi or I cook," Kutcher said. "I have someone that cooks for me... that's the best thing ever. I just want to show up and I want my house to be like a hotel... so I want to have a couple of options. ... I like to have a couple of options."
And does Moore, she of the famously maintained figure, actually eat?
"What do you mean does she eat?" said Kutcher. "Of course she eats!"
Moore's three children with actor Bruce Willis are nearly grown now. The youngest is 16.
McFadden asked Kutcher whether he wanted to have a biological baby.
"I don't know," he said. "It's I don't know.
"There is something attractive about our third girl gaining some independence. I get to walk the dogs in the morning because she can drive herself to school now. There is a level of independence that we've never had since our relationship started, and an ability to spend time together doing things that we might want to take advantage of, because in our relationship we've always had kids.
"And having Bruce as such a great partner in raising the kids affords us a lot. There is something very attractive about what we can do in the world and for the world... given that responsibility in a different place."
McFadden noted that Moore is now 47 and asked whether her biological clock wasn't ticking.
"I think my wife is a genetic freak," Kutcher said. "... I'm not worried."
Kutcher uses his social media prowess against the paparazzi that is constantly stalking his family.
"It means if I'm gonna be in a zoo, I want the keys to the cage," he said.
Instead of allowing the tabloid media to leak personal information about his relationship with Moore, he does it himself.
"We create a zone," Kutcher said. "We know exactly where we want the zone to be. We have an agreement with each other. We have an agreement with the people around us. We know what it is. ... Ninety percent of the stuff that I post has nothing to do with me."
But oh! that 10 percent. Kutcher once posted a photo of Moore's bottom, and tweeted, "Watching my wife steam my suit while in a bikini, I love God."
Kutcher said he is "1,000 percent certain that I am less exposed now, because I expose what I want to expose when I want to expose it."