As only one person essayed our little puzzle-joke, and got the wrong answer, we shall have to reveal the solution ourselves: it is because, like Superman (albeit in the guise of Clark Kent), he has been on or in Lois Lane! Still don’t get it? Check out his old address on Crackpot Central (Natural Philosophy Alliance):
Stop Press, late honorable mention: “because he is just one step away from wearing his underpants outside of his trousers”. Nice try, no coconut.