The game is simple: make a statement that over top the statement of the previous poster (and somehow related). e.g. 1st poster: I saw a mouse as big as a cat 2nd poster: That's nothing, I saw a mouse that can swallow a cat. 3rd poster: That's nothing, I saw a mouse that can squash a cat-eating mouse with the pinky of his left paw. 4th poster....
If it got staled or if you can't over top the previous poster, you can simply start a new topic...
Let's start, shall we?
I have seen the smallest arachnid in the world. Yesterday, I saw a spider as small as a grain of rice.