I have seen this game on another forum and I think it's kinda nice.
You simply post what the two people who posted above you have in common with each other. The two posters above you shouldn't contain yourself.
Obviously, the first 2 posts in this thread are going to be pointless. So someone needs to make one more post and the game can start in post 3.Example:
user 1: post
user 2: post
user 3: they joined the same month
user 1: they both like Pokémon
user 4: they have the same location