I call this game secret sentences, I learned it in college. It works with most age groups except for the ones who can't write any sentences.
Every pulls a page out of their notebook.
-Everybody writes a sentence at the very top of their page starting with "One day..."
-Then they fold the piece of paper at the very top so that it covers their sentence.
-They pass their paper to the person behind them (or to their right/left)
-They write a new sentence and fold the paper again and pass it.
When you run out of paper, you have the students read the end result. It's usually pretty funny.
You can have them write stories that have those sentences in them, or have them edit the grammar so that the sentences make sense together.
If they have trouble writing sentences or coming up with ideas, write words on the board, like dancing/running/going to the bathroom, to spur their ideas.
Hope that helps...