This is a variation on "what's the next line", but in this game, you give the first line and the next person has to make up the the follow-on line. For instance, the first person might give:
"I must go down to sea again, to the lonely sea and the sky"
and the next person would finish it off with their own composition, eg
"And all I ask is a luxury yacht, and hope that pigs might fly"
So I'll give another line, for someone to compose a suitable follow-on. And then that person will give another line from a poem for someone else to finish off
I wandered lonely as a cloud That floats on high o'er vales and hills,