So this may already exist, but if it does, it is long dead. So yeah.
In this thread, we write a story together. Each poster creates a sentence to add on to the previous sentence. And it all comes together.
Keep tabs on what has happened in the story. These can get complicated.
Well, it is nonsensical anyway, might as well put it in the title.
I'll start:
There once was a castle high in the clouds.