Imagine you're at the movies with your friends. You have some in-jokes and you rib each other for fun. Then, someone approaches your group with the Encyclopedia Yourfriendsica. He has studied the banter. He pretends that he's been one of your friends all along, using your in-jokes–often incorrectly. When someone makes a joke in a weird way, he corrects him with the textbook definition of your in-joke.
Eventually, more of them join your group. Eventually, your friends leave, and the group becomes a group of people impersonating your group of friends. The cycle continues indefinitely until the theater goes out of business.