Why do Your Characters Work Together?

At the beginning of this campaign, all of your characters will work for the Carnival of Wonder.  So, perhaps you think I've already answered the title's question.  But, I have not.  :-)

Yes, you all work for the Carnival, and you all travel on the three ships that take the Carnival from port to port, from show to show.  But, what BONDS your characters?  Why would they turn to each other specifically for help?  What short history might they share that explains why they trust one another when things get hairy?  When its time to get some shit done, why do each other these characters include each other in the task?

And these questions are for you, dear players, to answer.  You are all experienced players, and you can all come up with dozens of cool characters at a moments notice.  So, I know you will each have an interesting character.  But, I'm seriously asking that you guys share your character concepts, and start riffing some ideas for how your characters know each other, and why you are willing to perform tasks together as a subset of the Carnival scene?

If trouble is afoot, why does this handful of characters pull together.  This might be a challenging question, depending on the character concepts.  But, I think it will be worth meeting that challenge.  :-)