Fillion said that:
The secret of creating an epic hero is allowing the hero to fail. The age of the hero that's, "I know just who to call. He's the best man that ever lived." That era of hero is over. The Rambo that cannot fail. The super-invulnerable, can throw a knife at a hundred yards at a dead... We need a hero who's a real man who can actually fail. Indiana Jones was my first experience with that. There's a guy who got punched, and beat up and abused and bruised, and cut and stuck - and then wins in the end. That's the guy I like. And I think that's the secret to an epic hero.