Well, here's a pleasant surprise. This is a "documentary" on the making of Halo 4 that runs for over 10 minutes. You'd think such a clip would be full of agonising monologues by developers, and it is, but instead of just focusing on talking heads you're also seeing a ton of of in-game and cinematic footage.
And when you're not? There's genuinely interesting sequences of stuff like the art and motion-capture teams at work. So this is well worth a watch!