With some practice writing messages to each other, students are ready to use their imagination and write stories. I explained that a long time ago they didn't have TVs or movies for entertainment so they told each other stories. One common story was told to explain the world around them, especially why animals looked the way they did. (See "Just So Stories" by Rudyard Kipling or "Mother Westwind Stories" by Thornton Burgess.)
Students were given a small book made out of a regular (8 1/2" x 11") folded in quarters like a greeting card with a picture of a bunny on the front who had no tail. After reading some examples of stories ( e.g. "How the Camel got his Hump and Why the Bear Has a Stumpy Tail) students would write a story about "How the Bunny got a Fluffy Tail". As an incentive students got a cotton ball to glue on their bunny. Students would come up with ideas like "the bunny planted tail seeds and grew a tail" or "the bunny glued on some cotton candy for a tail".
What I learned: Children are reticent to make up their own stories but with a little practice and encouragement they can write delightful tales.