What made them all fall down?

One sunny May afternoon, four friends decided to spend the day outside. One by one at each of their houses they put on their most flexible athletic clothes, gathered their roller blades and headed out to a near by park. A few minutes later all four of them pulled into the park's parking lot. They swiftly put on their roller blades and began to skate up to the sidewalk. Some of the girls were quicker than the others but they all made sure to stay close to each other. As they skated they told jokes, stories and just enjoyed each others company while getting great exercise. As four girls glided around their three mile long journey around the lake they felt a great release of stress among themselves. The weather and stress free enviroment of the lake made them feel at ease. Eventually the girls got so caught up in the fact that they were having so much fun that they completely forgot that they were still roller blading. Without paying attention all four of them ran over a big, long, snake like stick that was in the middle of the path. One by one the girls fell to the ground after tripping over the stick. To their surprise, no one got intensly hurt. Nothing more than a few scrapes and scuffs were on their skin after the great fall. As the girls laid on the ground after falling they found humor in the situation and started to laugh. Now it is fifteen years later and the four girls are still great friends. Every time they get together the story of how they all fell down gets brought up and they share a great laugh over the great memory they share.