Party game, like Chinese whispers. Everyone gets in a line, and each person inserts a hand (right or left) into the rectum of the person in front of them. The person at the back then starts with a well known phrase (or a film title, or the name of a book) and, using sign language, communicates the phrase to the inner arse lining of the person in front, who passes it up the line as they then understand it. And so on. When it gets to the front of the line, that person speaks out loud the phrase they think it is, and the person at the back tells them what it started as. Much hilarity ensues.
Jesus Christ my arse is still bleeding from the Chinese fisters we were playing last night. Stan started out with "I'm not the pheasant plucker, I'm the pheasant plucker's son," and I ended up with "Fuck your mother yourself, you cabbage faced tosspot." Brilliant!