Open a mainstream comic book today, and you'll find a virtual rainbow of diversity. Many of the most vivid characters come in just about every shape and color. And it's no wonder: They're aliens.

People are a different matter. With some notable exceptions, superheroes still tend to be lily white -- and male -- under those tights and capes. "We can tolerate inhuman diversity but not human diversity," said Kim De Vries, a writing lecturer at the Massachusetts Institute of Technology who studies the small number of Asian main characters in comic books.