Description
This is a nice handle to structure scenes. One of the players is the Narrator. He has a (mimed) typewriter and starts the scene by reading aloud as he types. As soon as the Narrator has given a few elements, the players take over and start playing the scene.At any point, the Narrator can take over again, perhaps switch to another location, introduce new character, provide tilts or flashbacks.
Variations
When a scene goes bad, the Narrator can mime ripping a couple of pages of his story apart, and restart the scene (or the story). 
People with dogs are cowards c`se they don`t have the guts to bite others themselves --- August Strindberg