This game is played by creating a parallel universe with one difference to this one. The next poster will then state the result due to the difference, and make his/her own universe.
Example:
User 1: There is a parallel universe where people greet each other by smashing their knees together.
User 2: As a result, humans are no longer able to walk. There is a parallel universe where men have breasts.
There is a parallel universe where the sky is bright red.
As a result, everybody speaks sign language and ends up going to war over a misunderstanding with a race of people who do have tongues. There is a parallel universe where cats are as intelligent as humans (South Park!).