I think it was the moment somebody suggested it–the moment [Disney chief executive] Bob Iger saw Item 47, the DVD short directed by Louis D’Esposito. It was brought to me as, “We’ve crafted this Marvel deal, and we think there’s a SHIELD show.” And I just went, “Oh yeah, totally. That makes perfect sense.” Because SHIELD is fancy but it’s not over the top end-of-the-world superhero stuff, it’s a little bit more man on the ground. And then: “We think we want Clark [Gregg].” I said, “But will that be a problem for, you know, The Avengers?” If [Agent Coulson] died, we want to honor that and not make that movie retroactively cheesy. So I said, “Well, here’s what you do”–and what we did in the pilot was the exact thing I pitched. It’s not my first time bringing somebody back to life. It’s not my fourth.
Joss Whedon on why he thought SHIELD would work as a series (X)