A follow-up movie of two already successful movies oozes difficultly. A follow-up movie of one of the highest-grossing movies of all time oozes near impossible. That’s Iron Man 3, acting as both the sequel to Iron Man 2, released in 2010, and Marvel’s The Avengers, released last summer. Set to be essentially the first movie in the “second wave” of the Marvel Cinematic Universe, Iron Man 3 has a lot on its apparent shoulders. It’s a sequel, an introduction, and a conclusion.