I once ran a freeform game for some friends during a camping trip, I think there were 5 players. I had each one create a character (high concept framework, one great "attribute," one poor "attribute," and three "skills" or things they were good at). So for example, the "Xenobiologist" was and inquisitive bookworm with good intelligence and poor courage, who was good at bio-science, computers, and math. Easy.
I then had each player come up with a character secret and tell it to the person on their left, including how that person knew their secret. So the Xenobiologist was herself an alien-hybrid, and the Cyborg knew because he had been her bodyguard since she had started working for "The Lab."
Finally, once they were all finished, I had each person pass their character to the person on their right, at which point we began play.
Everyone loved that twist, and we had a blast.