Fatherhood has changed Brad Pitt — and all for the better. "It's the greatest thing I've ever taken on," the actor told ABC's Good Morning America. "It's the most difficult, the most rewarding and the most fun. I think this is the greatest thing I could possibly achieve, and hats off to all the parents out there." Brad also talks about the sadness that permeates the Missouri prairie culture he grew up in. "It's something that I feel in my grandparents, in the people I've met, in a Southern way of life. It's something pervasive." But his children have lifted that sadness. "They say the funniest things I've ever heard. They're the funniest people I've ever met." And he's got another blessing in his partner, Angelina Jolie. "One of the things I'm most happy about for my kids is that they have a mother, I think, because she's amazing," he says.