Not sure how clear the thread title is, so here's the basics of it. It's pretty simple, post something that the avatar of the last person who posted says about him/her.
The last person who posted has this avatar.
I could reply with: "He must like apples!" or "He must like the color red!"
Pretty much everything and anything goes, as long as it's not insulting or disrespectful towards age, gender, religions, beliefs, etc, etc....well, you guys get the idea.