These are very often widely circulated stories that are passed on from one person to another. Often, these are very frightening stories which are supposed to have really happened; whether they did or not, urban legends are meant to be believed. The stories have been told and retold so many times that they have become a part of popular mythology. A very popular urban legend in the U.S is that there are alligators living in sewers. Another one is that there is always a killer hiding in the back seat of a car.