I like the idea of a
Noodle Incident origin--give a name to an unspecified event in the past that brought the team together, then let them flesh it out via references whenever it seems sufficiently weird and amusing.
Example: The team was brought together by something they refer to as "the McGrath run".
1) The team is hunting (and being hunted by) a failed attempt at genetically engineering a unicorn. The result is armored, carnivorous, sentient, and pissed off (like the not-unicorns in P. C. Hodgell's Kencyrath novels). "Hey, this reminds me of the day we met!"
2) An improbable plan is suggested for the current run, and the troll street sam says, "Look, I told you after the McGrath run that I was
never wearing a tutu again."
3) The team is stumped. One ventures cautiously, "We could ask McGrath." Everyone else threatens to shoot him.
4) Something goes wrong--anything from a cyberzombie attack to the soykaf tasting a little off--and someone says, "Damn you, McGrath, this is all your fault."
If you want, after a while you could piece together the references and try to figure out what the incident actually was--maybe even do a flashback run with the team's starting builds--or you could just leave it a mystery and keep elaborating on it.
(McGrath, by the way, is my current character's fixer. Yes, it's all his fault.)
QUOTE (Acme @ Aug 27 2010, 06:39 PM)

I'll be starting a story soon that kinda grew out of backstory, the first guy's character is basically following after his father's exploits. As we sorta figured things out, the father basically turned into this playboy, and we figured that four of the five characters will end up being half-siblings because of the first guy's father and that part of the getting together will be figuring this out. I'm almost trying to convince the fifth guy too but that might be pulling teeth..
Something very like this happened by accident in the Pathfinder campaign I'm playing in. We didn't coordinate character creation beyond telling each other what classes we were going to play, and one of the available campaign traits (pieces of pre-written character backstory that come with perks) was "Finding Haleen", which set the character up to be searching for his missing sister, Haleen.
You guessed it. All but one player picked Finding Haleen...which meant that she had a human brother, a half-elf brother, and a half-djinn brother. Later, one player dropped and was replaced...by a guy who also independently picked the same trait. So Haleen acquired a half-orc brother as well. We're thinking of getting the party chartered as "The Brothers of Haleen", and suspect that their father is a minor fertility god of some kind.