True Scary Story

This is why you should never tell scary campfire stories if you're a fictional character.

The horrifying story that either turns out to be true or has its audience (and most likely the teller) initially not totally believing it's true, but as time goes by, things around them start to suggest more and more that the story that they heard is true. Either way, the True Scary Story will reach a point where the Horror Monster of the story at least looks like it came to life and tries to attack the audience of its story. At this point, the plot can diverge down two paths:

A) The story is true. The Monster is real. The audience is in danger and must fight the Monster or run for their lives.

B) The story isn't true. The Monster is actually someone friendly. The audience is not in danger and has no need to fight.