It's not peter pan exactly. How it works in that movie is toons are actors. He's just the guy who was hired to play Peter Pan as a kid and then got thrown out of the business like trash once he grew some stubble, which is why he went bad.

"Y’know, I got my big break when I was just a kid. I got cast in the biggest movie in the world, as the boy who wouldn’t grow up, Peter Pan. I’d never been so happy in my entire life! Then I got older, and they threw me away like I was nothing."