A sneak peek at the cover of Marvel's new picture book All the Hulk Feels reveals Bruce Banner's fight with his emotions.

Edward Norton played the role of Dr. Bruce Banner, who transforms into the emerald superhero whenever he gets angry - a rare genetic disorder caused after being exposed to gamma radiation.

These make sense, but there are other theories. One particularly funny comment is that parking makes Bruce Banner so angry that thinking about this causes him to turn into the Hulk. This leads to ...

He’s big, we won’t like it when he’s angry, and, of course, he’s very, very green. But that’s not the only hue Bruce Banner, or several other characters to take on the irradiated moniker ...