I'm busy preparing a Teenage Mutant Ninja Turtles game using the Marvel Heroic Roleplaying (MHR) system. It was suggested to me that I use Master Splinter as an Unlockable, but I'm not really sure how that would work. Slightly related, I'm also thinking of making April and Casey Unlockables in the same way.
I haven't played a game of MHR yet, so it will be my first time.