The Superman of today and the Superman that first appeared in 1938 are very different characters. While some of the important stuff is in place—Clark Kent, Lois Lane, and the tights—one of the more well-known bits of Superman trivia is that most of the stuff strongly associated with Superman didn’t come along until later. Originally, Superman couldn’t fly, he didn’t have heat vision or freeze breath. (To be fair, a lot of modern Superman stories are strangely embarrassed by that power for some reason.) And much of what becomes familiar hasn’t quite taken its final form yet: Krypton and Metropolis are both unnamed, The Daily Planet is The Daily Star.
Oh, and Superman is a total prick.