Basically one poster asks a question, the next person has to come up with a snappy or stupid answer and a new question.
EX:
Poster 1
Q: Why is the sky green?
Poster 2
A: Because I put something special in your brownies.
Q: Where have all the flowers gone?
Q: Where have all the flowers gone?
Etc, etc, etc.
I'll lead you all with the first question:
Q: A canner can can anything that he can but a canner can't can a can, can he?