13. The "Hulkalo"
One of the most amazing parts of The Avengers was the fact that the Hulk finally looked like Bruce Banner; it's hard not to be blown away by the special effects. Behind the scenes though, concept artists initially struggled to fulfil Joss Whedon's wish of having a Hulk who looked both like Mark Ruffalo and the classic comic book version of the character. Combining these was a challenge, and talented artist Ryan Meinderding would later reveal that when they finally realised that the actor's face lent itself well to that of the Hulk's, they nicknamed their creation the "Hulkalo". It's lucky for Mark that he looks like the Hulk then... well, sort of!