"Marvel started cranking out a new crop of movies, each featuring a different character, and fans began to realize that they hinted at a wider crossover potential. Stark had Captain America’s shield in his house. The bad guy in The Incredible Hulk got injected with a version of the supersoldier serum that created Captain America. It wasn’t that hard; Marvel was there to help the writers with a whole basket of Easter eggs: paramilitary agencies, Nazi scientists, magic cubes, secret formulas, and so on. The moviemakers started watching one another’s rough cuts and consulting with a “creative committee” of Marvel Comics writers. “In the first Iron Man, the Easter eggs were simply inside jokes for the Marvel faithful,” Favreau says. “By the time the second one rolled around, part of the agenda was to build toward The Avengers."