OK, ready for your prompt?
A family of four (mother, father, son, daughter). Living room. And one of them comes into the house with the new puppy. And something crazy happens. Write the scene. Don't lose any of the five characters (you didn't forget the puppy, did you!). All of them have a part. They all have something to say, something to do, they're all a part of whatever it is that happens. Pay special attention to your writing of dialogue and actions.
Plan out your story first, doesn't have to be long, but think about a lot of questions first. Or I don't care, dive right in.
