Here is Romney’s rough drawing and process work for the Avenger’s. It was one of his favorite scenes because he got to illustrate his childhood heroes!
Once the assets have been designed and drawn, Amelia rigs them as puppets in AE and begins animating. After completing a first pass and getting notes, she cleans up the arcs and makes the timing a little more snappy, working on one character at a time. Once the animation is approved, the background is added and voila! The Avengers kick some butt.