Just make up a story. You are restricted to four words per post. The next poster continues the story and so on.
Post 1: There once was a
Post 2: Hippo, who loved to
Post 3: Eat garlic. But one
Post 4: day... something really bad
etc... Take in concideration I made up a really cheesy ... and weird story for the example.
Let's get this going shall we?
There once was a