Baby George, who will someday be the king of the United Kingdom but for now is more occupied with keeping his parents up at night is "a bit of a rascal," William said.
"He either reminds me of my brother or me when I was younger, I'm not sure, but he's doing very well at the moment," the prince said of his son, born July 22. "He's growing quite quickly actually. But he's a little fighter -- he wriggles around quite a lot and he doesn't want to go to sleep that much."
William said that, though he's enjoying his new role as dad, he's also looking forward to getting back into his routine as a search-and-rescue helicopter pilot.
"Well, as a few fathers might know, I'm actually quite looking forward to going back to work (to) get some sleep," he said. "So I'm just hoping the first few shifts I go back I don't have any night jobs."
And that's not all he has in common with commoner new dads: Despite the cheering crowds and the international broadcast cameras, William said he was thrilled to put his son on display.
"I think more shock was the feeling I felt, but I was on such a high anyway, and so was Catherine, about George that really we were happy to show him off to whoever wanted to see him," he said.
"As any new parent knows, you're only too happy to show off your new child and, you know, proclaim that he is the best looking or the best everything. It's nice that people want to see George -- I'm just glad he wasn't screaming his head off the whole way through."
And yes, he practiced putting in the car seat.
"Believe, me it wasn't my first time, and I know there's been some speculation about that," he said. "I had to practice, I really did -- I was terrified it was going to fall off or the door wasn't going to close properly."
The entire interview with CNN, "Prince William's Passion: New Father, New Hope," will air September 15 at 10 p.m. ET.