72. The Phantom Stranger gets an origin. And another one. And another. And another... (Secret Origins #10, 1987)
I think origin stories are a huge part of a character's potential success or failure. Even the average non-comics-reader-on-the-street knows Bruce Wayne's parents were murdered and Superman was sent to Earth as a baby from the dying planet Krypton. But what are you going to do about origins when you're faced with a character whose very essence is mystery of the unknown?
Well, in a rare instance of comics creators really getting things right and not violating the foundations of a character via retcon, DC offered readers a multiple choice for the Phantom Stranger's origins, thus leaving the mystery intact. Four different origin stories are presented in Showcase #10, and which one you choose as the "right one" (or perhaps you can bend logic in your mind to accept all four if you so choose) is dependent on your interpretation of the character.
As far as I know (granted my knowledge is shallow), this is the only time a character's been presented with multiple origins. I think that's a pretty unique storytelling device, and one very deserving of the Phantom Stranger.