[quote=@Dedonus]
For characters that have not been picked up yet, I would err on the side of keeping them vague so that others can pick them up.  I'm fine with Kal-El's application because it still allows a player to take liberties with the character.  [b]Yes, they have to adopt Jimmpy into their character background[/b], but they have free-reign with everything else.  This "rule" is really to protect the popular characters (like Iron Man).  If its a minor character, you can take more liberties if you are using them as an NPC.
[/quote]

To be fair, [b]that[/b] is a pretty big restriction. 

But as I say, the player would just need to accept that and deal with it.