Did You Hide The Body by Potzrebowski, McMillan and Co.
This is what happens when a group of cousins have access to a tape recorder when their parents are away for the evening.
The ages of the children involved in this recording range from nine to fourteen (with a brief spoken word from a three year old at the end).
The kids improvised their dialog and made up the story as they went along, only pausing the tape recorder to collectively decide how the story should proceed. The music and sound effects were also improvised by the children using a Casio SK-1 toy sampling keyboard. They even went so far as to create their own 'out takes' at the end.