This Is Not Vietnam, This Is Iron Man
While you’ll most likely come across hidden details about other films in the MCU or the original comic books, the filmmakers love referencing other movies that the actors played in. There’s a scene in Iron Man when Pepper Potts is looking through Obadiah’s computer for proof that he’s shady. When you through the scene frame by frame, you’ll discover something pretty awesome.

Jeff Bridges, a.k.a. The Dude, played Obadiah Stane, and there are multiple references to this in Iron Man. The package was addressed to MSC Lebowski, and the barcode has THE00DUDE on it. There are also a couple of memorable lines from The Big Lebowski if you read the special card instruction.