I’ve always liked this one, and it was a big hit last year in Forest’s booth at the NSWF. Here's how it works:
One person begins with a sentence (e.g., One day Little Johnny walked to the local shoe shop).
The next person tells of something unfortunate that happens (e.g., Unfortunately, Little Johnny was hit by a car.).
The following person contributes a fortunate event (e.g., Fortunately, the car was made entirely of marshmallows).
The fourth person will contribute an unfortunate event (e.g., Unfortunately, Johnny was allergic to marshmallows.)
The fifth person will contribute a fortunate event (e.g., Fortunately, Johnny didn't eat any of the car.), and the process is repeated
One day, a small child wandered into the Forest.