I am a huge fan of what Marvel has established. But when they first came to me, Thor and Captain America were not even close to being finished. I thought to myself, 'Okay, you have all these moving parts, but how can you possibly bring them together?' Iron Man, Hulk, Thor and Captain America don't seem like they could co-exist, and ultimately that is what intrigued me and made me think, 'This can be done and this should be done.' You can't put these characters in a movie together without a certain amount of humor. It's an inoculation against the unreality.