If you haven't already, it's worth going and tracking down their original rules post. They generally have it linked in either the new week's contest post or in the result one.

In my case, I failed to see the part of it where it said the entry needed to be totally original. While I'd say 99% of it was, the joke itself is well known and even published. So, even though I came up with 2000 words of backstory for our thieving convicts, the joke wasn't mine. I did get a door prize, though, which was very nice of them.

Yeah. It's strange, but the comedic juices flow when someone else is saying something. I have had some success when I've been writing in script form, or a dialogue back and forth between two imaginary people. I might have to go that route. I just need to shorten it up. Too much time for something that might not pay off. There's a bang for the buck quotient to be met. :)