Here is something I just thought up, and will post it here to give it a try.
So, pretty much, one posts something, and then others post what is related to it. I'll give an example.
1st Person: Scissors cut paper, so Paper is related.
2nd Person: Paper can give paper cuts, so Paper Cuts are related.
3rd Person: Paper cuts hurt, pain is hurting.
This can go on and on. Here is the starting topic: