The Anonymous at the chan sites have different games, which they play together. Some of games forces the Anonymous (often with obsessions) to join, games like “If you don’t post in this thread XXX will happen” (XXX replaced with a statement that tells something bad).
A game often played at chan sites is “You raff you ruse” (With a picture of an Asian person). This means “You laugh you lose” (according to many Anonymous, Asian people speaks like that). This game’s purpose is to get as many Anonymous to laugh as possible by mainly posting funny pictures, but also by writing comments.
“Walk in, see this, what do?” ((Often)With a picture of something abnormal) is a game posted many times on the sites. This game is about telling the OP and the other thread readers how you would react to the situation if you would walk into a room with the abnormal happening at that moment.
“Your face when XXX” (XXX replaced with a statement, riddle, whatever) is a game similar to “Walk in, see this, what do?”, but in this game, your mission is to post a picture of a reaction. This game often has a message to assign to other Anonymous, if the game’s name is “Your face when you realize XXX” (XXX replaced with a (sometimes) smart argument)
“Mindfuck” is a game played at chan sites. The purpose is to look at a picture of something that looks just normal, but in fact, it’s hiding something that makes you surprised once you find it. It’s often written “When you see it you’ll shit bricks”, which means that you will be surprised (there are other variants of that quote, but that’s irrelevant, because there are too many to mention). There are many trolls among the “Mindfuck” pictures and they are created when a newfag wants to post some OC (Original Content). These trolls are just annoying to the Anonymous since the pictures just are showing normal pictures without any hidden surprises.
Lurk around on chan sites, (protip: 4chan /b/) to see if you can find any interesting games.