Over in another thread, we've been discussing how having a clear sense of what is about to happen, what will happen, or where the story is headed can be an advantage to a group that wants their story and their scenes to be as coherent, powerful, aesthetically pleasing, or well-acted as possible.
In some ways, knowing what's coming and why can help us to do that better. If I know that your character will ultimately betray me, I can highlight that by making my character as pure, innocent, gullible, or well-meaning and self-sacrificing as possible, for instance, adding weight and drama to the eventual betrayal.
For you, dear reader (and I really hope to hear from @EmmatheExcrucian
on this, in particular):
What's the furthest you've ever gone in terms of "pre-writing" game scenes and events before actually playing through them? For instance, have you ever established lines of dialogue, particular "stage choreography" (a kiss, a slap, a touch, an entrance or an exit), or other details before actually playing through that moment?
Has anyone ever gone so far as to write a whole script and then to perform it?
If so, what was your experience with doing so? Did you ever "cross a line", and decide to never do so again? What parts of the experience added to your game and which parts detracted from your enjoyment?
(I should clarify that I'm talking about *shared* knowledge/preparation/brainstorming - something the group does together, in the open - not the kind of thing where one player has a plan they want to spring on the others, like a railroading GM.)