The film opens with Red Skull breaking into a church and stealing a hidden Tesseract. But why was it there in the first place? Is there a possibility it was a gift to the vikings by Odin himself? ...
With a metabolism 4X the average human's, the notion that his body wouldn't have wasted away doesn't make sense. Did the comics provide any explanation for how he was able to survive?
After the Avengers, Tony Stark drives off with the Hulk, hinting at them working together. There were references in between the movie where Stark offers Bruce Banner a chance to work with him. Also ...