First Steps" in the article below. Galactus, a skyscraper-sized, planet-eating cosmic being, may be the primary antagonist of "The Fantastic Four: First Steps," but no villain looms larger in the Marvel blockbuster than Doctor Doom (Robert Downey Jr.

But that all changes in the movie's post-credits scene, when the vibe shifts and suddenly there's a metal-masked stranger hanging out in the living room of the Baxter Building. If you've seen The Fantastic Four: First Steps and need some Reed Richards–level tutoring to figure out just what the heck is going on,