In some games, players can narrate a flashback for their character. This usually delivers a fictional and/or mechanical bonus in the current scene.
I love this idea, because it encourages people to develop their character’s backstory over a series of sessions (“Play to find out what had happened”). It also overcomes a practical limitation of collaborative improvisation: If the characters were real they would take steps to prepare for the situations they’re in.
Anyway, I’m working on a game about “80s buddy cop movies,” and flashbacks are essential to the genre. I’m curious to hear about games where you think this mechanic is well implemented.