7. Andy Serkis' Secret Role
Marvel has already confirmed that Andy Serkis will play Ulysses Klaw in Avengers: Age of Ultron, and it's been rumoured that his appearance here is going to set up a much larger role for his character in the Black Panther solo movie. However, it's also been revealed that the actor will be bringing someone or something to life with the use of motion capture. What that second role will be is unknown as of right now, and Joss Whedon will be hoping it remains a secret. Unfortunately, early screenings could result in the cat being let out of the bag much sooner than expected, especially if he ends up bringing a character to life who will somehow be pivotal to the future of the Marvel Cinematic Universe and Phase 3 plans.