Let loose a horde of rag-headed squirrels on the train...
It's not supposed to be a comedy...
The point of the story is as an exercise for me in developing character. I've got seven people with names, jobs, and a vague idea of their character and desires. Everything else I'll figure out as I go along.
With luck, by the end, no reader could tell that each person's character flaws were inspired by one of the seven deadly sins. Did you know that "sloth" is more correctly translated "apathy" or "hopelessness"?