and I feel like this has great potential.
1) Make a list of fifteen characters first, and keep it to yourself for the moment. (That way you're not leading the questions asked to fit the characters.)
2) Ask your flist to post questions in the comments.
'One, Nine, Fifteen and Three are chosen by a prophecy to save the world from Four. Do they succeed?'
'Under what circumstances might Five and Seven fall in love?'
'Which character on the list would you most want on your side in a zombie invasion?'
After your flist has asked enough questions, round them up and answer them using the characters you selected beforehand, then post them.
If you want a surprise, don't look at the comments?
Also, everyone should enjoy The Saga of Commander Dumbass
(to be read from the bottom up), as linked to me by Rosalind.ETA: I love crazy people.