Superman is an alien and he sometimes disguises himself as a human.
I bought Issue #1 of "Astro City" a few weeks ago on Comixology, when all the Superman-related comics were priced at a deep discount for the premiere of "Man of Steel". It's a really interesting decontruction (?) of superheroes, with the first chapter covering "Samaritan", clearly a Superman analogue. He's busy all day, flying around the world from disaster to disaster, never standing still to enjoy himself. He has a cover identity working as a fact-checker for a newspaper, but it makes no sense to me why he does this, as he has no time to socialize or be normal, locking his door & letting a computer from the future do his work while he is out being a hero. Has anyone else read this? Is there any explanation for why he bothers to "work" for the newspaper, other than "that's what Clark Kent does"?