How do you integrate Samuel L. Jackson showing up to talk about the Avengers in Iron Man? “During the production, we started saying to [director Jon] Favreau things like, ‘We think Sam Jackson is going to do this,’ and he’d say, ‘How the hell is that going to connect to the story?’ ” Kevin Feige, Marvel’s lead producer, told me at San Diego Comic-Con a couple of years ago. “And we’d say, ‘It doesn’t, so let’s put it at the end of the credits.’ ” Those sidewise glances at other stories used to be vestigial; in more current Marvel movies, they’re intrinsic. Want to know where Nick Fury gets the helicarrier that saves the day at the end of Avengers 2? You should’ve been watching the Agents of S.H.I.E.L.D. TV show.